PLS HELP i am not sure what to do here:)

Question

How many liters of 70% alcohol solution and 20% alcohol solution must be mixed to obtain 20 liters of 60% alcohol solution?

You need ___liters of 70% solution and ____ liters of 40% solution.

Answer 1

70 -40 = 30

40-20 = 20

3/2 times as much 20% as 70%

3/2 = 12/8

12 Liters of 20%

8 Liters of 70%