Riddle: Jack went to school, and the following conversation ensued between him and his teacher. Teacher: Jack, how old are you? Jack : I don’t know, but I know am half my mother's age. Teacher : So how old is your mum? Jack: I don’t know but I know she's 5 years younger than my dad. Teacher: Wow! so how old is your dad? Jack: I don’t know, but I know the sum of all our ages is 80. Hmmmm, can you solve this riddle for the teacher?