Explanation:
If x is the volume of 25% solution, and y is the volume of 72% solution, then:
x + y = 85
0.25x + 0.72y = 0.40(85)
Solve the system of equations using substitution or elimination:
0.25x + 0.72(85 − x) = 0.40(85)
0.25x + 61.2 − 0.72x = 34
27.2 = 0.47x
x ≈ 57.9
y ≈ 27.1
Misty needs 57.9 ounces of 25% solution and 27.1 ounces of 72% solution.