Tad was delivering lunch to a local office building. His first delivery was to the middle floor of the building. He then took th elevator up 4 floors for the next delivery, down 6 floors for his third delivery, and up 7 floors for his final delivery. He was then on the top floor of the building. How many floors were in this building?

Answer 1

x+4-6+7= 5

5+5=10