Question 295939
    A chemist has 600 milliliters of a solution that is half acid. She needs a solution that is 70% acid. How many milliliters of acid she should add?
.
Let x = milliliters of acid added
then
x + .50(600) = .70(600+x)
x + 300 = 420 + .70x
.30x + 300 = 420
.30x = 120
x = 400 milliliters