Answer:
1) He was given a good piece of advice by his friends.
or
A good piece of advice was given to him by his friends.
2) He said he had been asked twice by them
or
He had been asked twiced about them he said.
3) A telegram was sent to her brother by me
or
A telegram was sent by me to her brother
4) The rule will be explained to him by them
5) My brother had to be operated by them
6) The plan was agreed upon by them
7) A party is being given by me this week
8) The girl's doll have been broken by the boys
9) No notice of his words was taken by them
10) He is always laughed at by his friends
11) By the time the director came the letter had been already typed by her
12) The project was worked out by them last week
13) The tree planting project will be sponsered by them
14) Was the window broken by your brother?
15) All the mistakes have been corrected by us
16) The front door of the house was locked by him
17) The instructions must be obeyed by everybody
18) When were the tickets bought by them?
19) Finally he was persuaded to agree by them
20) His new book will soon be published by them
21) Have the invitations been sent by them yet?
22) Before using the machine the instructions must be studied by you
23) The wallet was lost by me the day before
24) Have the telegrams already been sent by you
25) This kind of dictionaries can be found in that shop by you
Explanation: