Working a word problem backwards

Question

A burglar trying to escape police got on the elevator in a tall building. He went up 8 floors, down 4 floors, up 3 floors, down 7 floors, and down 2 floors. If he finished on floor 20, what floor did he start on?

Answer 1

Assume he started on floor n.  The given information translates into

 

n + 8 - 4 + 3 - 7 - 2 = 20

 

Can you solve for n and finish?