I'm not the best in the class.
Mark does not / doesn't do homework in the evening. (do homework: làm bài tập VN)
We don't play football after school.
You don't run fast.
=> Công thức chung:
S + am/is/are + not + adj.
S + don't + V (S: You, I, We, They,...)
S + doesn't + V (S: He, She, It, tên riêng,...)
do not = don't
does not = doesn't