Ответ:

1. he won't pass the exam if you don't help him prepare.

2. As soon as the guests gather, we will tell them the news.

3. When will you know the results? - When the teacher checks our papers.

4. I wonder if John will join us when we tell him about the trip.

5. Before the baby goes to bed, Mom will give him a bath.

6. In case he's not home, I'll stop by later.

7. I have no idea when the next meeting will be.

8. After the movie is over, we'll go for a walk.

9. If the weather is nice, we will go to the beach.

10. I hope that while I'm sleeping, the temperature will go down.

11. Please find out if they will go to the theater with us.

12. I won't buy anything until I have saved some money.

13. He says that when he comes back from vacation, he will organize a party.

14. I'll let you know as soon as it's ready.

15. While it's raining, I'll read or watch TV.

16. I'll wait until you get back.

17. I'm not sure if he'll write me, but if he does, I'll be sure to answer.

18. I feel like if we go on vacation together, we'll have a great time