1) We are painting our house at the moment.
=) Our house are bering painted at the moment.
2) An ambulance took the sick man to hospital.
=) The sick man was taken to hospital by an ambulance.
3) Visitors must leave umbrellas and sticks in the cloakroom.
=) Umbrellas and sticks must be left.
4) They make these actificial flowers of silk.
=) These artificial flowers of silk're made.
5) You should practice English everyday.
=) English should be practiced everyday.
6) Has someone posted the letters?
=) Have the letters been posted?
7) The police will ask you several questions.
=) You'll be asked several questions by the police.
8) My little brother has drunk all the milk in the fridge.
=)  All the milk in the fridge has been drunk by my little brother.
(Good luck to you!!!)

1, We are painting our house at the moment
--> Our house are bering painted at the moment
2, An ambulance took the sick man to hospital
--> The sick man was taken to hospital by an ambulance
3, Visitors must leave umbrellas and sticks in the cloakroom
--> Umbrellas and sticks must be left
4, They make these actificial flowers of silk
--> These artificial flowers of silk are made.
5, You should practice English everyday
--> English should be practiced everyday