Question

Fallow the patterns
as if/ as though

Exemplo:
He doesn´t know anything about computers but he acts like an expert
He acts as if he were an expert with computers.

1- He is very thin but eats like he was fat.
2- She isn´t the only girl in the house but uses the bathroom like she was.
3- They are not very clever, but they act like they are.
4- My sister acts like she´s a movie star.
5- You´re eating like this is the last meal you´ll ever eat.
6- To keep from getting nervous, just imagine the audience in their underwear.

Answer 1

Hi there!
He eats as if he was fat. 
She uses the bathroom as though she was the only girl in the house.
They act as though they were very clever.
My sister acts as if she were a movie star.
You´re eating as if this was the last meal you´ll ever eat.
To keep from getting nervous, just imagine as if the audience were in their underwear.  
 
Espero ter ajudado! :)