согласуйте времена:
1) When you ( to finish) this exercise, you will read the text.
2) The post man (to say) he would come earlier next time.
3) The boy sees that the dog often (to drink) water.

When you to finish this exercise, you will read the text. А зачем инфинитив?

1) When you finish this exercise, you will read the text. 2) The post man said he would come earlier next time. 3) The boy sees that the dog often drinks water.

1. finish2. said3. drinks