Question 758135
A chemist has one solution that is 25% alcohol and another that is 75% alcohol. How much of each must she use to make 14 liters of a solution that is 50% alcohol? 
.
Let x = amount (liters) of 25%
then
14-x = amount (liters) of 75%
.
.25x + .75(14-x) = .50(14)
.25x + 10.5-.75x = 7
10.5-.50x = 7
-.50x = -3.5
x = 7 liters (25% alcohol)
.
amount of 75% alcohol:
14-x = 14-7 = 7 liters