1.   Mary types letters in the office.

Letter are typed in the office

2.   His father will help you tomorrow.

You will be helped by his father tomorrow

3.   Science and technology have changed human life.

Human life has been changed by Science and technology

4.   They are learning English in the room.

English is being learned in the room.

5.   Nothing can change my mind.

My mind can't be changed

6.   No one had told me about it.

I hadn't been told about it

7.   My students will bring the children home.

The children will be brought home by my students

8.   Somebody has taken some of my books away.

 Some of my books has been taken away

9.   They will hold the meeting before May Day.

The meeting will be hold before May Day 

10.  The boys broke the window and took away some pictures.

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

11.   People spend a lot of money on advertising every day.

A lot of money is spent on advertising every day.

12.   The children looked at the woman with a red hat.

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

13.   They have provided the victims with food and clothing.

The victims have been provided with food and clothing.

14.   They have provided the victims with food and clothing.

The victims have been provided with food and clothing.

15.  They have provided the victims with food and clothing.

The victims have been provided with food and clothing.

16.   After class, one of the students always erases the chalk board

After class, the chalk board is always erased by one of the students

17.  Will you invite her to your wedding party?

Will she be invited to your wedding party ?

18.  Has Tom finished the work?

Has the work been finished by Tom?

19.   Did the teacher give some exercises?

Were some exercises given by the teacher ?

20.   Have they changed the window of the laboratory?

Has the window of the laboratory been changed ?