Question 785335
Mollie's brother = 2x-3

Mollie = x

The sum = x + 2x-3

The sum = 24

x + 2x-3 = 24

3x - 3 = 24

3x = 27

x = 9

Mollie is 9 years old. 

Her brother is 2(9)-3 or 15 years old.