the police asked each of us about his movements on the right of the crime

someone has already told him to report for duty at six

no one can do anything unless someone gives us more information

people are spending far more money on food now than they spent 10 years ago

they will say nothing more about the matter if someone returns the stolen gun

it is high time someone told him to stop behaving like a child

chuyển chủ động sang bị động

the librarion said that they were starting a new system because people were not returning books 

chuyển chủ động sang bị động 

M=x²/6-x

tim gia tri cua x de m >=0