Question

The sum of the ages of two sisters is 12 years, and the difference in their ages is 6 years. What are their ages?

Answer 1

They are 9 and 3.

Explanation:

Let one of them be `a` years and the other be `b` years
So `a+b=12` equation 1
And `a-b=6` equation 2

Add equation 1 and equation 2
`2a=18`
`a=9`

`a+b=12`
So `b=3`