Ответ:

1. older, the oldest

2.more difficult, the most difficult

3.larger, the largest

4.happier, the happiest

5.farther, the farthest

6.hotter, the hottest

7.heavier, the heaviest

8.worse, the worst

9.more careful, the most careful

10.prettier, the prettiest

11.more important, the most important

12.better, the best