A pineapple drink contains 15% pineapple juice. How much pure pineapple juice should be added to 8 quarts of the drink to obtain a mixture containing 50% pineapple juice?

Answer:
5.6 quarts
Step-by-step explanation:
x + .15(8) = .50(8+x)
x + 1.2 = 4
.50x + 1.2 = 4
.50x = 2.8
x = 2.8/.50
x = 5.6 quarts