Answer:
1) Sí, le escribo.
2) Sí, le escriben.
3) Sí, me escriben.
4) Sí, nos escriben
Explanation: (Translation)
1) Do you write your grandma letters?
Yes, I write to her.
2) Do the students write letters for the professors?
Yes, they write to him.
3) Do your friends write your letters?
Yes, they write to me.
4) Do your grandparents send you all letters?
Yes, they write to us.
Hope this helps! :))