1, I have heard her sing this song several times.

-> She has been heard to sing this song several times by me.

2, People saw him steal your car.

-> He was seen to steal your car.

3, The teacher is watching them work.

-> They are being watched to work by the teacher.

4, He won't let you do that silly thing again.

-> You won't be let to do that silly thing again.

5, Peole don;t make the children work hard.

-> The children aren't made to work hard.