I really need help with these problems I don't understand it. Can someone help?

Answer:
the oldest is 31 years old, the youngest is 15.5 years old, and the middle is 10.5 years old
Step-by-step explanation:
First you take the two halves from 10.5 and 15.5 and add the two halves to get 1. So you would make an equation. The one I used was (10+1)=(15+31)= 57