Passive voice:
1. My sister gave me a new pair of jeans on my fifteenth birthday.
-> I was given a new pair of jeans on my fifteenth birthday by my sister.
2. They have sold their car to pay their debt.
-> Their car has been sold to pay their debt.
3. Did people make jeans two hundred years ago?
-> Were jeans made two hundred years ago?
4. He sent me a letter yesterday.
-> I was sent a letter yesterday.
5. We did our homework two days ago.
-> Our homework was done two days ago.
6. Did she finish the work yesterday?
-> Was the work finished yesterday?
7. What did they do last night?
-> What was done last night?
8. I had written two letters before.
-> Two letters had been written by me before.
9. He had bought a new car
-> A new car had been bought.
10. We have done 4 tests since last week
-> 4 tests have been done since last week.