Please knock at the door before you come into the room .（句意不变）
Don‘t_come into_ the room _before_ knocking at the door.
This rope is three times longer than that one.（简单句）
This rope is four times __as__ ___long__ ___as___ that one.
I have no idea where we'll go.(简单句)
I have no idea where ___to____ __go___
最后一句能改成简单句的就加两个词,用不到三个词.