Jordan is another employee at the same coffee shop. He has worked there longer than Gabe and earns $3 more per hour than Gabe.

so what is the question asking for?

Step-by-step explanation:

We have 20% and 70% salt solutions.
We need 9 liters of 50% salt solution.
"t" is liters of twenty % solution "s" is liters of seventy % solution

A) t + s = 9
B) .2t + .7s = (.5 * 9)
Multiplying A) by -.2
A) -.2t + -.2s = -1.8 Adding that to B)
B) .2t + .7s = (.5 * 9)
.5s = 2.7
s = 5.4 liters of 70% salt

A) t + 5.4 = 9

t = 3.6 liters of 20% salt

Source:
http://www.1728.org/mixture.htm