Answer:
16 liters of 70% alcohol
4 liters of 20% alcohol
Step-by-step explanation:
Let x = volume of 70% alcohol and y = volume of 20% alcohol. Since we need total of 20 liters, the first equation is x + y = 20. Next, calculate the amount of alcohol in the 20 liters of 60% alcohol. 60% is equivalent to 0.6, so there is 20*0.6 = 12 liters of alcohol in the 20 liter solution. Therefore the second equation is 0.7x + 0.2y = 12.
x + y = 20
0.7x + 0.2y = 12
2x + 2y = 40
7x + 2y = 120
-5x = -80
x = 16
16 + y = 20
y = 4
