Learn Hardcore Japanese: kouhai ga kaigi no siryou wo tyanto youisite kurete, tasukatta. - My junior prepared the meeting materials properly for me, which was helpful.

It’s the benefactive verb くれる, meaning “to do something for me/us.” 用意してくれて means “(someone) prepared (it) for me,” implying the action benefited the speaker. Without くれて (just 用意して or 用意した), it would lack that “for my sake” nuance.

Who is the subject of 助かった? It just says “was helped.”

The subject is omitted but understood as “I” (or “we”), because くれて signals the action benefited the speaker/in-group. So it’s effectively “I was helped / It was a big help (to me).”

Why is くれて in te-form? What does the 〜て、 do between the clauses?

The te-form here links clauses and often implies cause or reason. 用意してくれて、助かった ≈ “(They) prepared it for me, so that helped.” You could also write it with an explicit connector: 用意してくれたので/から、助かった or 用意してくれたおかげで、助かった (stronger “thanks to”).

Why use が after 後輩 instead of は?

後輩が marks “junior colleague” as the grammatical subject/doer, often presenting new or focused information.
後輩は would make “junior colleague” the topic, which can sound more contrastive or background-setting. Both can be correct; が feels natural for reporting what someone did in this moment.

Can I explicitly mark the recipient of the favor?

Yes: 後輩が私に会議の資料を用意してくれて、助かった。 Usually 私に is omitted because くれる already implies the benefit to the speaker. You can replace 私に with another recipient, e.g., うちのチームに.

How is this different from using もらう?

Vてくれる: the subject is the giver; the speaker is the beneficiary.
Example: 後輩が資料を用意してくれて、助かった。
Vてもらう: the subject is the receiver (often the speaker).
Example: 私は後輩に資料を用意してもらって、助かった。
Both mean you received a favor; they differ in grammatical viewpoint.

What exactly does ちゃんと mean here?

It’s an adverb meaning “properly,” “as expected,” “without sloppiness.” It modifies the verb 用意する: 資料をちゃんと用意する = “prepare the materials properly.” Synonyms: きちんと (slightly more formal), しっかり (thorough/solid).

Where can I place ちゃんと in the sentence?

Natural: 資料をちゃんと用意する (most common), ちゃんと資料を用意する (also fine).
Don’t say ちゃんと資料 unless you change it to an adjective phrase: ちゃんとした資料 (“proper materials”), which changes the meaning.

Is the tense consistent? Why is 助かった past, but くれて isn’t?

In Japanese, the final verb sets the overall tense. The linked clause with te-form (くれて) doesn’t carry tense by itself. 助かった makes the whole statement past: “(They) did X for me, and that helped.”

Could I just say 用意してくれた。助かった。 as two sentences?

Yes. Or combine more formally: 用意してくれたので、助かりました。 The original te-link is concise and natural in speech and casual writing.

Is 助かった the same as 助けられた?

No.

助かった: “(I) was saved/it helped (me).” No explicit agent; it’s a general relief/gratitude statement.
助けられた: passive “(I) was saved by (someone).” If you want to name the savior, use Xに助けられた.
Here, using 〜してくれて、助かった highlights the specific helpful action done for you.

How would I make this polite or honorific?

Polite: 後輩が会議の資料をちゃんと用意してくれて、助かりました。
If the doer is a superior, use honorific くださる: 部長が資料を用意してくださって、助かりました。
Or humble from your viewpoint: 部長に資料を用意していただいて、助かりました。

Can I say 助かったです?

No. Use plain 助かった (casual) or polite 助かりました. Attaching です to the plain past of a verb like this is ungrammatical. (Exception you may know: よかったです is idiomatic, but 助かったです isn’t.)

What does 会議の資料 mean, and can I say 会議資料?

会議の資料 = “materials for the meeting.” 会議資料 is a compound noun with the same meaning, common in written/business contexts. Both are fine; 会議資料 can sound a bit more formal/terse.

Is ちゃんと necessary?

No. Removing it yields a neutral statement: 後輩が会議の資料を用意してくれて、助かった。 Including ちゃんと adds the nuance that it was done properly/fully.

What are the readings of the key words?

後輩: こうはい
会議: かいぎ
資料: しりょう
用意して: よういして
くれて: くれて
助かった: たすかった

Is the comma after くれて required? And what about the spaces?

The comma is optional and indicates a slight pause. Standard Japanese doesn’t use spaces between words; they were likely added for teaching/clarity.

Could I replace 助かった with something like ありがたかった?

Yes. 〜してくれて、ありがたかった also expresses gratitude (“I was grateful that…”). 助かった emphasizes relief/helpfulness; ありがたかった emphasizes appreciation.

Why is くれる used for a junior colleague? Would it be rude for a senior?

くれる is neutral-casual benefactive and is fine for peers/juniors. For actions by a superior toward you, switch to honorific くださる (e.g., 〜してくださって). Using plain くれる for a superior can sound disrespectful.