Here are the responses for the prompts:

6. Their grandmother told us this story.
→ We **were told this story by their grandmother**.

7. Tim ordered this train ticket for his mother.
→ This train ticket **was ordered by Tim for his mother**.

8. You didn’t show me the special cameras.
→ I **wasn’t shown the special cameras by you**.

9. It's pity that you are not here now.
→ I wish **you were here now**.

10. You can't be truly happy unless you learn to laugh at things.
→ If I **learn to laugh at things, I can be truly happy**.

11. Write to her, or she will forget you.
→ If **you don’t write to her, she will forget you**.

12. He doesn’t like his job, so he isn't happy.
→ If **he liked his job, he would be happy**.

13. She doesn't do her homework, so she doesn't get good marks.
→ If **she did her homework, she would get good marks**.

14. He is upset so he won't come to the party.
→ If **he weren’t upset, he would come to the party**.

15. Stop talking or you will wake the children up.
→ Unless **you stop talking, you will wake the children up**.

IV. Words for revision.

5. If he **gives** up smoking as his doctor orders, he will be soon well again.
6. More tourists would come to this country if it **had** a better climate.
7. The police have **arrested** five suspects.
10. No one **believes** this story.
11. If I **knew** his address, I’d give it to you.
12. If you (not pass) your driving test unless you drive more carefully.
13. If I had a typewriter, I **would type** it myself.
14. If he worked more slowly, he (not make) so many mistakes.