Two old friends, Jack and Bill, meet after a long time. Three kids Jack: Hey, how are you man? Bill: Not bad, got married and I have three kids now. Jack: That?s awesome. How old are they? Bill: The product of their ages is 72 and the sum of their ages is the same as your birth date. Jack: Cool? But I still don?t know. Bill: My eldest kid just started taking piano lessons. Jack: Oh now I get it.