The jones family has 3 children.
amy’s age plus betty’s age is 29 years. amy’s plus carl’s age is 27 years. betty’s plus carl’s age is 22 years. what is the difference between the oldest child and the youngest child is?

Amy = x
Betty = y
Carl = z
x + y = 29
x + z = 27
y + z = 22
y = 29 - x
z = 27 - x
29 - x + 27 - x = 22
-2x + 56 = 22
-2x = - 34
x = 17
y = 12
z = 10
Oldest child is Amy (17) and youngest child is Carl (10)
17 - 10 = 7
The difference between oldest child and youngest child is 7 years.