Let Alex's height = a.
Let Ben'x height = b.
a + b = 130
b - a = b/3
Subtract b/3 from both sides int he second equation to obtain:
(2/3)b - a = 0
Add this new equation to the first original equation.
(5/3)b = 130
b = 130 * 3/5
b = 78
a + b = 130
a + 78 = 130
a = 130 - 78
a = 52
Answer: Alex's height is 52 inches, and Ben's height is 78 inches.
