Ответ:
1. He will feel better as soon he does not eat trash food.
2. If she worked hard, she would earn some money for the journey to the seaside.
3. He would write better, if he read more books.
4. If you wore this jacket today, you would be cold.
5. If she knows the secret, she will never tell anyone.
6. They will help me if it is necessary.
7. Do not open the door if someone rings the doorbell.
8. If she had English practice abroad, she would speak better.
9. We would catch the last bus if we left at once.
10. If you went on a diet, you would lose weight.