there are 128 fluid ounces in 1 gallon, that means that 25 gallons is 25 * 128 = 3200 ounces.
so if we know that for 20 ounces is 3.54, how much will it be for 3200 ounces?
[tex]\begin{array}{ccll} \$ & oz\\ \cline{1-2} 3.54 & 20\\ x& 3200 \end{array} \implies \cfrac{3.54}{x}=\cfrac{20}{3200}\implies \cfrac{3.54}{x}=\cfrac{1}{160}\implies 566.4=x[/tex]
