Sarah collects stamps and keeps them in envelopes. She had 9 envelopes with a certain number of stamps, s, in each envelope. She sells 3 of the envelopes. Which expression represents the number of stamps Sarah has left?

Explain how you got the answer:

Question

Sarah collects stamps and keeps them in envelopes. She had 9 envelopes with a certain number of stamps, s, in each envelope. She sells 3 of the envelopes. Which expression represents the number of stamps Sarah has left?

Explain how you got the answer:

anonymous · Answer

Do you see how we get the expression 

9s 

for the number of stamps?

anonymous · Answer

Yea.

anonymous · Answer

So what is the expression that represents the number of stamps sarah has left. These are the choices.

9s - 3 

(9+3)s

9s- 3s

9s - s - 3.

Which is the correct answer? 

And how did you get the answer.