To know the best deal, we have to know which one gives us the least cost per gallon.
To do that we divide the price by the quantity or volume.
A) $56 for 25 gallons
B) $32.05 for 15 gallons
C) $51.29 for 23 gallons
D) $22.50 for 10 gallons
The best deal is B: $32.05 for 15 gallons, because it offers a price per gallon that is lower than the others.