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?

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