Question

How many liters of a 20% alcohol solution must be mixed with 50 liters of a 70% alcohol solution to get a 40% alcohol solution?

Answer 1

0.2x + 0.7(50) = 0.4(x + 50)
0.2x + 35 = 0.4x + 20
35 = 0.2x + 20
15 = 0.2x
75 liters = x