Hi, How many quarts of pure antifreeze must be added to 2 quarts of a 30% antifreeze solution to obtain a 40% antifreeze solution? x + .30(2QT) = .40(2QT + x) x + .30(2QT) = .40(2QT) + .40x .60x = .10(2Qt) x = .10(2Qt)/.60