Question

A girl is 21 years old and her brother is a third her age. When the girl is 36, what will be the age of her brother?

Answer 1

21 divided by 3 = 7

That means the brother is 14 years younger.

36 - 14 = 22

The brother will be 22 years old.

Answer 2

a third of 21=21/3=7

in how many years
36-21=15

in 15 years
7+15=22

age is 22