a. Theresa can't eat unless her mother lets her.
b. You can't earn more money unless you work harder.
c. You can't understand the lesson unless you listen carefully.More Examples:
If you aren't tired, let's go out.
Let's go out unless you are tired.
I will call the police or you will leave immediately.
Unless you leave immediately, I will call the police.
Ali must study harder or she won't pass the final exam.
Ali won't pass the final exam unless she studies harder.
If Not / Unless Conversion
You will stay home if you don't come with us.
You will stay home unless you come with us.
You can't win the lottery if you don't buy a ticket dad.
You can't win the lottery unless you buy a ticket dad.
I will trash your sandwich if you don't want to eat it.
I will trash the sandwich unless you want eat it.
I am not going to the party if Carol is not going.
I am not going to the party unless Carol is going.