An elevator is on the 9th floor. It goes down 7 floors, then up 3 floors, then up 8 floors. If the elevator is on the top floor, how many floors are there in the building? Let's be accurate as possible.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
From the 9th floor, the elevator went down to the 9 - 7 = 2nd floor. Then went up to the 2 + 3 = 5th floor. Then, went up to the 5 + 8 = 13th floor; hence there are 13 floors in the building.
The answer: 13.