A repairman purchased several furnace-blower motors for a total cost of $150. If his cost per motor had been $5 less, he could have purchased 1 additional motor. How many motors did he buy at the regular rate?

Answer 1

For x motors, $150, so each cost 150/x
For a cost of 150/x - 5, then there were x+1 motors, all for the same $150:

(x+1)(150/x - 5) = 150
x = 5

check:
5 @ $30 = 150
6 @ $25 = 150