Question

Mari and Jen each work 20 hours a week at different jobs. Mari earns twice as much as Jen. Together they earn $480. How much does each girl earn in a week?

Answer 1

We will call:
M=Mari
J=Jen

Initial equations:

M=2J
M+J=480
(the fact that they work 20 hours a week is not needed in this problem information)

Plug in:
2J+J=480
3J=480
J=160

Jen makes $160 a week.

Therefore:

M=2J
M=2(160)
M=320

Mari makes $320 per week
Jen makes $160 per week