Sure! Here are the sentences rewritten in passive voice:

**EXERCISE 21:**
1. Some advice will be given to you by Doctor Brown.
2. The hotel will be redecorated by a famous designer.
3. "E.T." was directed by Steven Spielberg.
4. The crystal vase has been broken by someone.
5. He has been brought up to be polite by his parents.
6. Penicillin was discovered by Fleming.
7. The product will be advertised on television by them.
8. That film is being remade by someone.
9. That picture was painted by Picasso.

**EXERCISE 22:**
1. The bathroom must be left tidy.
2. This plant should be watered daily.
3. The garage ought to be painted by our neighbor.
4. These books have to be returned to the library by me.
5. Your cigarettes must be extinguished.
6. This shirt must be dry-cleaned.
7. You will be paid in ten days.
8. Your health can be improved with more exercise.
9. The law must be obeyed.
10. The kitchen floor is going to be mopped by the cleaner.

**EXERCISE 23:**
1. She is being helped with the housework by someone.
2. Our door had been broken down by someone.
3. He was chosen as the best actor of the year.
4. I was robbed by a pickpocket.
5. Mrs. Green was sent a parcel by the mail-order company.
6. The child is being chased by a dog.
7. An invitation was sent to me by my friend.
8. A new barn is being built by the farmer.
9. Some letters have been given to Mrs. Jones by the secretary.
10. He had already been given a ticket for illegal parking by the traffic warden.

**EXERCISE 24:**
1. The electrician has already been paid for his work by someone.
2. French was taught to him and a dictionary was given to him by them.
3. When we first met, I had already been offered a job at the bank.
4. The stranger was requested to leave the meeting by a man.
5. The rest of us were asked to be there at eight o'clock by a young woman.
6. All the dinner had been eaten before the conversation was finished by them.
7. By whom was it written?
8. A special edition for children has been written by the author.
9. Were you interested by the idea?
10. Why wasn’t the roof mended before it fell in by them?

Let me know if there's anything else you'd like!