Respuesta :

Let Joy be x years old

Joy's brother's age is 3 years older than twice joy's age.
Joy's Brother = 2x + 3

The sum of Joy's age and her brother's age is 24.
x + 2x + 3 = 24
3x + 3 = 24
3x = 24 - 3
3x = 21
x = 21 
÷ 3 
x = 7

Joy:
x = 7

Brother:
2x + 3 = 2(7) + 3 = 17

Difference in their age = 17 - 7 = 10 years

They are 10 years apart.