#1 : 8 pints in a gallon
#2: if he bought 8 pints which equal a gallon he'd spend $4.72 because you multiply .59 * 8
#3: he'd save .83 cents because when you multiply .59*8 you get get 4.72 and the gallon which is 3.89 is cheaper so you subtract 4.72-3.89 and get .83 cents