how many gallons of 70% alcohol solution must be mixed with 30 gallons of 23% solution to obtain a solution that is 60% alcohol?

How do I solve this problem?

2 answers

let the amount to be added be x gal

.7x + .23(30) = .6(30+x)
times 100
70x + 23(30) = 60(30+x)
70x + 690 = 1800 + 60x
10x = 1110
x = 111 gallons
Together a baseball and a football weigh 2.25 pounds, the baseball and a soccer ball weigh 1.25 pounds, and the football and the soccer ball weigh 2.50 pounds. How much does each of the balls weigh?