So I think you have to find 11% of 24 and that is 11/100 x 24 = 2.64$. Then you reduce it to the real price 24-2.64= 21.36$ (the new prize). I might be completly wrong but I hope this helps
B. is the answer because he can just refill the 1 gallon jug to eventually measure out 3 gallons!