Answer
We need to mix 12 gallons of the 15% salt solution.
Work Step by Step
Let X represent the amount of the 15% salt solution that is to be mixed.
The second solution is 8 gallons.
That means that the final solution will be 8 + X gallons.
We use the following guideline to solve this problem:
Amount of salt in the first solution + Amount of salt in the second solution = Amount of salt in final solution.
15% $\times$ X + 20% $\times$ 8 = 17% $\times$ (8 + X)
$.15 \times X + .2 \times 8 = .17 \times (8+X)$
0.15X + 1.6 = 1.36 + 0.17X
0.24 = 0.02X
Divide both sides by 0.02
X = 12
We need to mix 12 gallons of the 15% salt solution.
