want a solution containing 10% acid with one containing 15% acid to obtain a 20once solution containing 12% how many ounces of 10% should be used

Question

How many ounces of 10% solution should be Used 

Answer 1

Let x = the number of ounces of the solution containing 10% acid

Let y = the number of ounces of the solution containing 15% acid

x + y = 20      y = 20 - x

.10x + .15y + .12(20)

10x + 15y = 12(20)

10x + 15y = 240

10x + 15(20 - x) = 240

10x + 300 - 15x = 240

-5x = -60

x = 12 ounces