Đáp án:

13  All of us weren't shown round the house
14  Ten dollars was owed to me
15 You could have been seen from the house if it hadn't been so dark
16 Were you explained this point ?

17 Prozen food isn't sold at that shop
18 I want to know what sort of research is being done
19 Are you sure that you aren't watched by anyone ?
20 I haven't asked that question before.
21  The results of the exam will be announced on Monday
22  The workers were promised higher wages

13. All of us weren't shown round the house.
14. Ten dollars was owed to me.
15 You could have been seen from the house if it hadn't been so dark.
17.Were you explained this point ?
18. I want to know what sort of research is being done.
19. Are you sure that you aren't watched by anyone ?
20. I haven't asked that question before. 
21. The results of the exam will be announced on Monday.
22. The workers were promised higher wages.