Math help! Please explain how to do this!?

here's the idea for the first one: Sally paints 1/4 of a house in an hour, and John 1/6 of a house in an hour, so together they paint 1/4 + 1/6 of a house in an hour. 1/4 + 1/6 = 5/12 of a house. Thus when they work together they need 12/5 of an hour. You can work out what this is in hours and minutes.