Question 1068757
The Jones family has 3 children.  Amy's age plus Betty's age is 29.  Amy's age plus Carl's age is 27.  Betty's age and Carl's age is 22.  What is the difference between the oldest and the youngest child?
<pre>Let Amy’s, Betty’s, and Carl’s ages, be A, B, and C, respectively
Then: 
A + B     = 29 ------- eq (i)
A     + C = 27 ------- eq (ii)
    B + C = 22 ------- eq (iii)
    B – C = 2 -------- Subtract eq (ii) from eq (i) ------- eq (iv)
       2B = 24 ------- Adding eqs (iv) & (iii)
B, or Betty is {{{matrix(1,4, 24/2, or, 12, years-old)}}}

12 + C = 22 ------- Substituting 12 for B in eq (iii)
C, or Carl is: 22 – 12, or 10 years-old

A + 12 = 29 ------- Substituting 12 for B in eq (i)
A, or Amy’s age = 29 – 12, or 17

Difference between the oldest (Amy), at 17, and the youngest (Carl), at 10 = {{{highlight_green(matrix(1,4, "17 - 10,", or, 7, years))}}}