1.  It is believed that 13 is an unlucky number.
2. It is known that English is an international language./English is known to be an international language.
3. She has heard this song to sing several times.
4. He was seen to steal your car. 
5. John is said to be the brightest student in class./ It is said that John is the brightest student in class. 
6. Let your book be opened.
7. I was adviced to sell that house. 
8. It is dangerous for the short cut to be taken.
9. He is thought to have died a natural death.
10. You won't be let to do that silly thing again.