Переведите предложения из активного в пассивный залог
1) We hear a sound of a piano in the hall 
2) I bought this book a week ago
3) The secretary has already brought these letters
4) They went home after they had finished the work
5) Our scientists are examining this problem now
6) My mother taught him English
7) I sent her brother a telegram
8) My friends always take care of my sister
9) His friends always laught at him
10) We have never lived in this house

1) A sound of piano is heard in the hall by us.2) This book was bought by me a week ago.3) These letters have already been brought by the secretary.4) They went home after the work had been finished by them.5) This problem is being examed by our scientists now.6) He was taught English by my mother.7) Her brother was sent a telegram by me.8) My sister is always taken care of by my friends.9) He is always laughed at by his friends.10) This house has never been lived in by us.