Two brilliant logicians, NAME_1 and NAME_2, meet at a conference. Many years ago they once lived together in a shared flat; since then they have not seen each other. So they go to a bar to have a beer together.

At some point, NAME_1 starts talking about his family. He informs NAME_2 that he has three children. When NAME_2 asks how old they are, NAME_1 - quite the logician - gives him only three clues: 

If you multiply the ages of my three children together, the result is 36. 
If you add their ages, the result is equal to the house number of our student flat-share at the time. 
My oldest child has red hair.