37. He used to write letters to keep in touch with her when he lived far from her.
Letters used to be write letters to keep in touch with her when he lived far from her.
38. Because of the bad condition of the house, the city council decided to pull it down.
$\text{Because the condition of the house was bad,the city council decided to pull it down.}$
39. He last went to the cinema two months ago.
$\text{He hasn't go to the cinema for two months.}$
40. I won’t take part in the volunteer program because I don’t have enough free time.
$\text{If I had enough free time,I would take part in the volunteer program.}$