Поставь глагол в форму Past Simple или Past Continuous:
What Nick (to do) when you came to his place?
When Kate (to open) the door, the children (to dance) round the fir-tree.
When Tom (to cross) the street, he (to fall).
What you (to do) when I rang you up?
I (not to sleep) at nine o'clock yesterday.
When I (to go) to school, I (to meet) my friend.​