1 They didn't send the letter yesterday
2 He didn't become famous
3 They didn't used to go there
4 We didn't used to spend much money on cassettes
5 She didn't used to play the piano much.
6 I didn't used to go to the theatre every Sunday
7 He didn't used to travel by train
8 They didn't have to take a taxi
9 He won't understand it
10 We shan't walk to the station