11. He orders us to clean the floor.

=> We are ordered to clean the floor by him

12. You must see it to belive it.

=> It must be seen to belive it

13. People belive that the earth stood still.

=> It's belived that the earth stood still.

14.People son't make the children work hard.

=> The children aren't made to work hard

15. Don't do that silly thing again.

=> That silly thing isn't done again

16. They begged us to help him.

=> We are begged to help him by them