With the information, you gave me, I know that n is a variable that needs to be solved for. If you did not provide enough information, for some reason and that was the wrong concept, comment below and I'll help you out.
Also a rule to keep in mind is "What you do to one side, you do to the other."
The image attached shows you how the problem is done.
If you have any questions, just comment them below! :)
