Turn from Active into Passive.
5. Someone seems to have made a terrible

5. Someone seems to have made a terrible mistake.
A terrible mistake seems to have been made by someone.
6. You will have to pull down this building as you have not complied with the town planning regulations.
This building will have to be pulled down as the town planning regulations haven’t been complied with by you.
7. He expected us to offer him the job.
The job was expected to be offered to him (by us). 
8. Children couldn’t have done all this damage.
All this damage couldn’t have been done by children.
9. We shall have to find someone to take her place.
Someone will have to be found to take her place.
10. The New Arts Gallery is to exhibit my paintings.
My paintings are to be exhibited by the New Arts Gallery.