1.He was doing his homework at 9 p.m yesterday
->His homework was being done by him at 9p.m yesterday
2. The police were following the suspects.
->The suspects were being followed by the police
3. They were washing their car when I came.
->Their car was being washed when i came 
4. They were making some cakes-
.->Some cakes were being made
5. I was taking my dog to the park
->My dog was being taken by me to the park