The present tense action verb do is used with the subjects I and you.
I do my homework.
You do your homework.
We also use the verb do with the plural subjects we and they.
We do our homework.
They do their homework.
With singular subjects, the verb do changes to does.
Mary does her homework. She does her homework.
John does his homework. He does his homework.
The past tense form of the verb do is the verb did. We use did for the past tense with both singular and plural subjects.
I did my homework.
You did your homework.
We did our homework.
They did their homework.
Mary did her homework.
John did his homework.
The present tense verb do changes to does with certain subjects. The past tense verb did is used for all subjects.
▶It’s your turn. Decide if this sentence blank needs do, does, or did: Mary ____ her homework last night. Did you figure it out? Good for you!