wǒ yòng qiānbǐ xiě bǐjì, xiěcuò le kěyǐ mǎshàng yòng xiàngpí cādiào.

Because the sentence describes two different actions involving a tool:

• 用铅笔写笔记 = use a pencil to write notes
• 用橡皮擦掉 = use an eraser to rub it off / erase it

In Mandarin, 用 + tool + verb is a very common pattern.

So:

• 用铅笔写 = write with a pencil
• 用橡皮擦掉 = erase with an eraser

This is very natural Chinese.

Mandarin often puts the method or instrument before the main verb.

So the structure is:

• 我 = I
• 用铅笔 = using a pencil
• 写笔记 = write notes

So literally it is closer to:

• I using a pencil write notes

This sounds strange in English, but it is normal in Chinese.

A useful pattern is:

Subject + 用 + tool + verb + object

For example:

• 我用手机看视频。 = I watch videos on my phone.
• 他用筷子吃饭。 = He eats with chopsticks.

It literally means write notes, but in natural English we usually translate it as take notes.

So:

• 写笔记 = write notes / take notes

This is a very common expression in Chinese.

For example:

• 上课的时候我会写笔记。 = I take notes during class.

写错了 is best understood as:

• 写 = write
• 错 = wrong
• 了 = marks a completed action or change of state

So 写错 is a verb + result complement structure:

• 写错 = write something incorrectly / make a mistake in writing

Then:

• 写错了 = wrote it wrong / made a writing mistake

So 写错 is not just a random two-syllable word to memorize by itself; it is a very common pattern:

verb + 错 = do something wrongly

Examples:

• 看错了 = saw it wrong / misread
• 说错了 = said it wrong
• 买错了 = bought the wrong thing

Because the sentence is talking about a mistake that has already happened, and then a possible next action.

• 写错了 = if you have written it wrong / once you write it wrong
• 可以马上用橡皮擦掉 = you can immediately erase it

So 了 appears with 写错了 because that part refers to a completed mistake.

But 擦掉 comes after 可以, which expresses ability or possibility, so it is not presented as a completed action here. It means:

• can erase it
• not erased it

If the erasing were also completed, then 了 might appear there too in another context.

Yes. In Chinese, the if idea is sometimes understood from context without using an explicit word like 如果.

Here:

• 写错了，可以马上用橡皮擦掉。

This naturally means something like:

• If I write something wrong, I can erase it right away.

Chinese often leaves this kind of relationship implicit when it is obvious.

You could also say it more explicitly:

• 如果写错了，可以马上用橡皮擦掉。

That would also be correct.

The object is omitted because it is already understood from context.

擦掉 means erase/rub off something, and here that something is:

• the mistaken writing
• the wrong character
• the wrong note
• the part that was written incorrectly

Chinese often omits objects when they are obvious.

A fuller version might be:

• 写错了可以马上用橡皮把它擦掉。
• If I write it wrong, I can erase it right away.

In the original sentence, 它 is simply left out because it is not necessary.

擦 by itself means wipe, rub, or erase, depending on context.

擦掉 adds the result complement 掉, which often suggests:

• removal
• getting rid of something
• causing something to disappear

So:

• 擦 = wipe/rub
• 擦掉 = wipe off / erase completely / rub off

Using 掉 makes the result clearer: the mistaken writing is removed.

This is a very common pattern in Mandarin:

• 删掉 = delete
• 扔掉 = throw away
• 洗掉 = wash off
• 忘掉 = forget

Here 可以 means can or be able to in a practical sense.

So:

• 可以马上用橡皮擦掉 = can immediately erase it with an eraser

Depending on context, 可以 can also mean:

• may
• it is okay to
• be allowed to

But in this sentence, the most natural meaning is simply can.

Because 马上 is an adverb meaning immediately / right away, and adverbs usually come before the verb phrase they modify.

So:

• 可以马上用橡皮擦掉
• can immediately erase it with an eraser

That placement is very normal.

You will often see this pattern:

modal verb + adverb + verb phrase

For example:

• 我可以马上去。 = I can go right away.
• 他会马上回来。 = He will come back immediately.

Sometimes both are possible, but they do not always sound exactly the same.

In this sentence, 可以马上用橡皮擦掉 is the most natural order.

• 可以 first highlights the idea of being able to
• 马上 then modifies the action 擦掉

If you say 马上可以, it may sound like you are emphasizing very soon it will become possible, which is a slightly different idea.

So for this sentence, it is better to keep:

• 可以马上用橡皮擦掉

Because Chinese often omits repeated subjects when they are easy to understand.

The full idea is:

• 我用铅笔写笔记，
• （我）写错了，（我）可以马上用橡皮擦掉。

The second and third 我 are omitted because they are obvious.

This is extremely common in Mandarin and makes the sentence sound natural rather than repetitive.

Yes. A fuller version with 把 would be:

• 写错了可以马上用橡皮把它擦掉。

This makes the object more explicit:

• 把它擦掉 = erase it

The original sentence leaves the object out, which is also very natural.

So:

• 用橡皮擦掉 = natural when the thing being erased is obvious
• 用橡皮把它擦掉 = more explicit

Both are correct.

It is a common word, especially in Mainland Mandarin, but there is some regional variation.

• In Mainland China, 橡皮 often means eraser
• In some places, especially depending on region, people may also say 橡皮擦

So learners should know both:

• 橡皮
• 橡皮擦

Both can mean eraser in everyday use.

Because 笔 is related to writing tools and writing.

• 铅笔 = pencil
• 笔记 = notes

Historically and semantically, 笔 has to do with writing instruments or writing.

So in these words:

• 铅笔 literally includes the idea of a writing tool
• 笔记 includes the idea of written notes

This kind of repeated character is very common in Chinese vocabulary and can help you remember related words.

Yes. A natural English translation would be something like:

• I use a pencil to take notes, and if I make a mistake, I can erase it right away with an eraser.

Or more casually:

• I take notes in pencil, so if I write something wrong, I can erase it immediately.

This is a good reminder that Chinese and English often organize the same idea differently, even when the meaning is straightforward.