TL:
S1+ V1+ that+ S2+ V2
1) It + be + PII+ that+ S2+ V2
2) S2+ be + PII+ to V/ have PII
1.people believed that the earth was centre of the universe.
It was believed that the earth was centre of the universe.
The earth was believed to have been centre of the universe.
2.people think that the driver had both legs broken in the crash.
It is thought that the drive had both legs broken in the crash.
The driver is thought to have been both legs broken in the crash.
3.people expect that the economy will grow by 2% in the coming year.
It is expected the economy will grow by 2% in the coming year.
The economy is expected to be grow by 2% in the coming year.
4. People say that only three people in the world can understand his theory.
It is said that only three people in the world can understand his theory.
Only three people in the world is said to be able to understand his theory.