Ответ:

1. I went to the library in order to return books that I had borrowed.

2. We didn't go to the amusement park so as not to be caught in the rain.

3. I agreed to go to the concert though I was tired.

4. Chris joined the gym so that to keep fit.

5. The food for the party will be prepared by Susan.

6. The school had been painted before the students returned from the summer holidays.

7. This exercise must be done within fifteen minutes.

8. Mike didn't pass the final exam, despite of the fact, that he studied hard.