Question

Jack had $80 more than Eric. When Jack spent $30, he found that the amount of money he had left was twice s much as Eric had. How much did the boys have altogether at the beginning?

Answer 1

First we define variables:
 x: amount of money Jack has
 y: amount of money Eric has
 We write the system of equations:
 x = y + 80
 x - 30 = 2y
 Solving the system we have:
 x = $130 
 y = $ 50
 Therefore, the amount of money they had at the beginning is:
 130 + 50 = $ 180
 Answer:
 the boys had $ 180 altogether at the beginning