1. Mary types letters in the office.

=> Letters are typed in the office by Mary.

2. His father will help you tomorrow.

=> You will be helped by his father tomorrrow.

3, Science and technology have completely changed human life.

=> The human life has completely been changed with science and technology.

4. Peter broke this bottle.

=> This bottle is broken by Peter.

5. They are learning English in the room. 

=> English is being learnt in the room .
 

6. My mind can't be changed.

7. I hadn't been told about it.

8. Her telephone number isn't known by me.

9. The children will be brought home by my students.

10. I was sent a present last week.

11. We were given more information by her.

12. All the workers of the plan were being instructed by the chief engineer.

13. Tea can't be made with cold water.

14. Some of my books have been taken away.

15. The meeting will be held before May Day.

16. The engine of the car has to be repaired.

17. The window was broken and some pictures were taken away by the boys.

18. A lot of money is spent on advertising every day.

19. A story is going to be told by teacher.

20. A cake is being cut with a sharp knife by Mary.

21. The woman with a red hat was looked at by the children.

22. The victims with food and clothing have been provided.

23. English is spoken in almost every corner of the world.

24. This machine mustn't be used after 5:30 p.m.

25. The chalk board is always erased by one of the students after class.