Learn Hardcore Japanese: kare ha daigakusei de, kyoukasyo wo tukatte yosyuu to hukusyuu wo suru you ni zibun de kimemasita. - He is a university student and decided for himself to use the textbook to do preparation and review.

So 大学生で ≈ “(being) a college student” and it links the background information to the main clause.
It’s similar to English: “He is a college student, and he decided…”

Why is there a comma after 大学生で? Could you drop it?

The comma just separates two clauses and makes the sentence easier to read:

Clause 1 (background): 彼は大学生で
Clause 2 (main action): 教科書を使って予習と復習をするように自分で決めました。

You can drop the comma in writing; it doesn’t change the grammar:

彼は大学生で教科書を使って予習と復習をするように自分で決めました。

The meaning and structure are the same; the comma is just for readability and a small pause in speech.

What is the difference between 教科書を使って and 教科書で here?

Both can be used, but the nuance is a little different.

教科書を使って予習と復習をする
Literally: “use the textbook and do preparation and review.”
- 使って is the te-form of 使う.
- It explicitly mentions the action “use,” so it feels like:
  “He (specifically) uses the textbook as a tool to do his prep and review.”
教科書で予習と復習をする
Here で marks the means / tool, so it’s like:
“He does his prep and review with the textbook / using the textbook.”

In many contexts, both are natural.
教科書を使って is slightly more explicit and deliberate: you are actually “using” it, not just vaguely “by means of” it.

What exactly is 使って doing grammatically?

使って is the te-form of the verb 使う (“to use”).

The te-form here has two roles at once:

Connecting actions
- 教科書を使って (and then) 予習と復習をする
  “Use the textbook and do preparation and review.”
Expressing method / means
- “Do preparation and review by using the textbook.”

So you can think of it as both “and” and “by doing” at the same time: “He uses the textbook and (by doing so) he prepares and reviews.”

Why do we have 予習と復習をする and not just 予習と復習する?

予習 and 復習 are both noun + する verbs:

予習する – to do preparation (study beforehand)
復習する – to review (study again afterwards)

You have several grammatically correct options:

予習と復習をする
- Treat 予習と復習 as one combined object of する.
- Very clear and neutral.
予習と復習する
- Omits を (often done in everyday speech).
- Also natural, especially in casual contexts.

So を here is not required, but it is totally normal and adds a bit of clarity and formality: “do preparation and review.”

There are two を in the sentence (教科書を and 復習を). Isn’t Japanese supposed to avoid “double を”?

Japanese avoids having two を that are both direct objects of the same verb.

But here, each を belongs to a different verb:

教科書を使って
- 教科書 is the object of 使って (from 使う).
予習と復習をする
- 予習と復習 is the object of する.

Because the sentence is really:

教科書を使って（→ 使う）
予習と復習をする（→ する）

there is no problem. The “no double を” idea only applies when you try to give one verb two direct objects, each marked by を.

What does ように mean in 予習と復習をするように自分で決めました?

Here ように connects the verb する to 決めました and forms the pattern:

V-辞書形 + ように決める
“to decide to (make it so that one will) V”

So:

予習と復習をするように決めました
≈ “He decided that he will do preparation and review / decided to make it a rule to do prep and review.”

Nuance points:

V + ようにする / V + ように決める often imply a habit, policy, or effort:
- 毎日運動するようにしています。
  “I try to exercise every day / I make sure to exercise every day.”
Compared to V + ことにする / 決める, ように can feel a bit more like “ensure / make sure that”, often about ongoing behavior.

So here, it’s not just a one-time decision; it can suggest setting a personal rule or habit about studying.

How is するように決めました different from something like することにしました?

Both express “deciding to do something,” but with slightly different flavors.

V-辞書形 + ことにする / ことにしました
- Fairly neutral “decide to do V.”
- Works well for single decisions:
  - 日本に留学することにしました。
    “I’ve decided to study abroad in Japan.”
V-辞書形 + ようにする / ように決める
- Often feels like:
  - “make it so that I (habitually) V,”
  - “decide to make an effort to V,”
  - “set it up so that V will happen.”
- Common for ongoing habits / policies:
  - 毎日日本語を勉強するようにしています。
    “I make sure to study Japanese every day.”

In your sentence, 予習と復習をするように自分で決めました leans toward: “He decided (for himself) that he will make a practice of doing preparation and review.”

What is the nuance of 自分で here? How is it different from 一人で?

自分で and 一人で both often translate as “by oneself,” but they focus on different things.

自分で
- Focus: by one’s own will / own effort / own responsibility.
- Typical meanings:
  - “personally,” “on one’s own initiative,” “without others doing it for you.”
- Here: 自分で決めました
  → “He decided by himself (without being told / without others deciding for him).”
一人で
- Focus: physically alone, without companions.
- e.g. 一人で映画を見ました。
  “I watched a movie alone.”

In this sentence, 自分で clearly modifies 決めました, emphasizing “he himself made the decision.”
If you wrote 一人で決めました, it would sound more like “he decided alone (without discussing it with others).”

Does 自分で mean he studies by himself or that he decided by himself?

In the given word order, it most naturally attaches to 決めました:

…予習と復習をするように自分で決めました。

So the default reading is:

自分で決めました – “He decided by himself.”

If you wanted to clearly say “He does the prep and review by himself,” you’d usually place 自分で closer to する:

彼は大学生で、自分で予習と復習をするように決めました。
彼は大学生で、予習と復習を自分でするように決めました。

Word order and proximity usually tell native speakers what 自分で is modifying.

Can I change the word order, like 予習と復習を教科書を使ってする instead of 教科書を使って予習と復習をする?

Yes, you can rearrange it, and both are grammatical, but the nuance shifts slightly.

Original:
- 教科書を使って予習と復習をする
  - Emphasis flows: “using the textbook → do prep and review.”
Variant:
- 予習と復習を教科書を使ってする
  - Emphasis flows: “prep and review → (and how?) using the textbook.”
  - Sounds a bit more “spoken,” slightly more marked.

Both are understandable and natural in context. Japanese word order is fairly flexible inside a clause, but:

Putting elements right before the verb (する) tends to highlight them.
The original is the most neutral and common ordering.

Why is it 彼は and not 彼が?

は marks the topic, while が marks the grammatical subject (with a focus nuance).

彼は大学生で…
- “As for him, he is a college student, and …”
- Sets 彼 as the general topic of the sentence.
- Very natural for introducing or talking about someone’s situation.

If you used 彼が, it would sound like you’re contrasting or focusing on “he” specifically, for example against someone else:

（みんな社会人だけど）彼が大学生で、…
“(Everyone else is already working, but) it’s he who is a college student, and …”

In a neutral description like this, 彼は is the most normal choice.

Why is 決めました in the past tense, even though his habit of studying might still continue?

In Japanese, decisions are typically expressed with the past tense when they were made at some point in time:

〜することにしました。 – “I decided to do ~.”
〜するように決めました。 – “I decided to make it so that I do ~.”

The decision itself happened in the past, even if the resulting plan or habit continues now.
This is similar to English “I decided” or sometimes “I’ve decided.”

If you wanted to focus more on the ongoing state of that decision/rule, you could see:

〜することにしています。 – “I make it a rule to do ~ / I’ve decided and (still) do ~.”
〜するようにしています。 – “I make sure to do ~ (as an ongoing habit).”

But for simply reporting “He decided (at some point)”, 決めました is exactly what you want.

What is the difference between 予習 and 復習?

Both are study-related, but they refer to different timing:

予習（よしゅう）
- Literally: “pre-study.”
- Studying material before class:
  - reading the textbook in advance,
  - checking vocabulary,
  - looking over upcoming grammar.
復習（ふくしゅう）
- Literally: “re-study.”
- Reviewing material after class:
  - going back over what was taught,
  - doing exercises again,
  - making sure you remember.

So together, 予習と復習 covers both preparation and review around each lesson.

Could I say 彼は大学生なので、教科書を使って… or 彼は大学生だし、教科書を使って… instead of 彼は大学生で、…?

Yes, but each choice adds a different nuance:

彼は大学生で、教科書を使って…
- Simple connection, fairly neutral.
- “He is a college student, and he uses a textbook to…”
彼は大学生なので、教科書を使って…
- なので = “because / since.”
- Now being a college student is presented as a reason for using the textbook.
- “Since he is a college student, he uses a textbook to…”
彼は大学生だし、教科書を使って…
- だし often means “and also / besides,” sometimes with a slightly casual tone.
- Suggests one of several reasons or pieces of information:
  - “He’s a college student and (among other things) he uses a textbook to…”

In your original sentence, で keeps it neutral: it just gives background (he’s a university student) and then states what he decided to do, without strongly saying “because.”

How would this sentence look in a casual style?

You mainly change the polite ます form to plain past, and optionally drop は if context is clear:

Polite:
- 彼は大学生で、教科書を使って予習と復習をするように自分で決めました。
Casual:
- 彼は大学生で、教科書を使って予習と復習をするように自分で決めた。
- Or even shorter in context:
  彼、大学生で、教科書を使って予習と復習をするように自分で決めた。

The grammar (で, を使って, ように, 自分で) all stay the same; only the politeness level changes.