1. He is my old friend.

(Can we use this one when one of my friends is very old though I met him one week ago?)

2. My favorite class is math class.
3. My favorite class is a math class.
(Which one is right? Are both right? )

4. I do my homework with her after school.

5. I do my homework after school with her.

6. After school, I do my homework with her.

(Are the three expressions grammatical?)

1. yes

2. yes
3. yes
4. yes
5. yes
6. yes.

Sra

1. The sentence "He is my old friend" can be a bit ambiguous because the word "old" can refer to both age and the length of the friendship. In this case, it is more common to interpret "old" as a long-standing friendship rather than referring to the person's age. However, if you want to emphasize that your friend is elderly, it might be more precise to say something like "He is my elderly friend" or "He is my friend who is much older than me, despite having recently met."

2. Both sentences 2 and 3 are grammatically correct, but they convey slightly different meanings. Sentence 2, "My favorite class is math class," implies that your favorite subject overall is mathematics. Sentence 3, "My favorite class is a math class," implies that among different math classes you may have, there is one particular math class that you enjoy the most.

4. The sentence "I do my homework with her after school" is grammatically correct. It implies that you and another person (her) do your homework together, and you do it after school.

5. The sentence "I do my homework after school with her" is grammatically correct as well. It has the same meaning as sentence 4, indicating that you do your homework after school, and you do it with another person (her).

6. The sentence "After school, I do my homework with her" is also grammatically correct. It indicates that after school, your first activity is doing homework, and you do it with another person (her).