A chemistry lab wants to prepare 300 liters of 25% acid solution. In stock he has 20% and 35% acid solutions. How many liters of each in stock mixture should he mix tp prepare a 300-liter mixture?
If we use x liters of 20% acid, then we use (300-x) liters of 35% acid. So, keeping track of the amount of acid in each part, we have
.20x + .35(300-x) = .25(300)