Sure! Here are the rewritten sentences for each prompt:

1. They haven’t seen each other since Mary’s wedding.
- The last time they saw each other was at Mary’s wedding.

2. It’s three years since I last spoke to her.
- I haven’t spoken to her for three years.

3. How long is it since you used the car?
- When did you last use the car?

4. We started living here 15 years ago.
- We have lived here for 15 years.

5. I’ve never eaten this kind of cake.
- It’s the first time I have eaten this kind of cake.

6. This is the best computer I have ever used.
- I have never used a better computer than this.

7. He hasn’t chatted with his classmates through the internet.
- It’s been ages since he chatted with his classmates through the internet.

8. How long is it since you used the car?
- When did you last use the car?

9. He has never played a computer game before.
- This is the first computer game he has ever played.

10. We haven’t seen her since we left university.
- The last time we saw her was when we left university.

11. The last time he came to the cinema was two months ago.
- He hasn’t come to the cinema for two months.

12. You are late again. You’ve already been late once this.
- It’s the second time you have been late.

13. I last saw Minh six months ago.
- I haven’t seen Minh for six months.

14. The last time Tom visited his uncle was two years ago.
- It’s been two years since Tom visited his uncle.

15. Hoa hasn’t written to her parents for three months.
- The last time Hoa wrote to her parents was three months ago.

16. The last time we ate this kind of food was in January.
- We haven’t eaten this kind of food since January.

Feel free to adjust any of the sentences as needed!