1: The Insurance Salesman

An insurance agent calls at a lady's house to collect her premium and suggests further policies for her three children. He asks their ages, to which she replies 'the product of their ages is 36; the sum of their ages is the number of the house next door.' The agent replies; 'I'll need more information than that.' 'Not if I tell you that it's my eldest child you can hear playing the piano.' How old were the children?