1. What is his opinion like?

2. What do you think his opinion is like?
- I don't agree with him about his opinion.
- I don't agree with him on/about the statement that his old master was careless.
- His opinion is wanterful.
(Are they all acceptable?)

3. His acting is great.
4. That makes two of us.
5. You can say that again.
6. I think so, too.
7. I agree with you.
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The last four sentences are the same in meaning, right?
Why is the expression in #4 used? Could you explain the meaning of #4? Thank you.

Note my corrections:

1. What is his opinion?
2. What do you think his opinion is?
- I don't agree with him about his opinion.
- I don't agree that his old master was careless.
- His opinion is wanterful. <~~Do you mean "wonderful"?

Sentences 3-7 are correct.
Sentences 4-7 mean about the same thing.
Sentence 4 is a colloquial way to say sentence 7. (The two people -- the speaker and the person being spoken to -- agree.)

1. What is his opinion like?

To understand someone's opinion, you would typically need to listen to or read what they have said or written on a particular topic. Their opinion refers to their viewpoint or belief about that topic.

2. What do you think his opinion is like?
When you are asked this question, you are being asked to speculate or share your own thoughts about someone else's opinion. You might base your answer on your knowledge of the person's beliefs or previous statements.

Regarding the sentences:
- "I don't agree with him about his opinion." This sentence is correct and means that you disagree with his opinion on a specific matter.
- "I don't agree with him on/about the statement that his old master was careless." This sentence is also acceptable and means that you disagree with the particular statement he made about his old master being careless.
- "His opinion is wanterful." This sentence contains a typo (wanterful), and the intended word may have been "wonderful." Nonetheless, this sentence is not grammatically correct and does not make sense.

3. His acting is great.
Yes, this sentence means that the person's acting is excellent or of high quality. It is a positive statement expressing admiration for the person's skills as an actor.

4. That makes two of us.
5. You can say that again.
6. I think so, too.
7. I agree with you.

These four sentences are similar in meaning and all convey agreement with a previous statement or sentiment expressed by someone else. They are commonly used to affirm that the speaker shares the same opinion or viewpoint as the person they are speaking to.

Regarding #4, "That makes two of us," it is an idiomatic expression indicating that the speaker holds the same opinion or feels the same way as the person they are addressing. It implies solidarity or agreement by suggesting that the speaker also shares the same sentiment.