Ответ:

1. If they don't understand the exercise, Mrs Wells will explain it again

2. If Tom paied  more attention, he would answer the question.

3. She will play better if she practises more.

5. James wouldn't cry if the doctor didn't give him an inaction.

6. if it doesn't rain so much, Mary will enjoy her walk

7. Tin wouldn't feel so sad if his girlfriend didn't cheat on him.

4 и 8 не видно