1. He couldn't get into the house because he (forget) his keys.
2. When he (write) all his postcards, he had to buy more stamps.
3. He remembered the story very well because he (read) the book several times.
4. By the time he (finish) his studies he wanted a holiday.
5. When I got home I discovered I (lose) my keys.
6. Ryan Patterson came up with his idea after he (visit) a fast food restaurant.
7. He was very hungry because he (not eat) since breakfast.
1)forgot
2)wrote
3)has read
4)had finished
5)lost
6)visited
7)hasn't eaten
вроде так, возможны ошибки