Three Brothers entered a shop, each needing a pair of shoes re-soled and a key cut. There are two assistants in the shop, both of whom work at the same speed. It takes 15 minutes to re-sole a pair of shoes and 5 minutes to cut a key. How quickly can they finish?
30 Minutes ( one assistant does 1 pair of shoes and 3 keys and the other does 2 pairs of shoes)