a solution of 67% soution is mixed with a solution o f57% to make 30 liters of a 59% solution. How many of each solution is used?

let the amount of the 67% solution be x L

then the amount of the 57% solution is 30-x L

.67x + .57(30-x) = .59(30)

solve for x, I suggest multiplying both sides by 100 to get rid of the decimals