Question 651716
How much of a 50% acid solution must be mixed with 50 gallons of a 12% acid solution to obtain a solution that is 40% acid? 
.
Let x = amount (gallons) of 50% acid added
then
.50x + .12(50) = .40(x+50)
.50x + 6 = .40x+20
.10x + 6 = 20
.10x = 14
x = 14/.10
x = 140 gallons