Step-by-step explanation:
85 ounces of 40% acid solution = 85 (0.4) = 34
Also, x + y = 85 ... (1)
0.72x + 0.25y = 34
72x + 25y = 3400 ...(2)
multiply eq (1) by 25, we get 25x + 25y = 2125 ... (3)
subtracting eq(2) and (3), we get 47x = 1275
x = 27.13 substitute in eq(1), we get
y = 57.87
Misty needs 27.13 ounces of 72% acid and 57.87% of 25% acid solution.