there are 4 quarts in one gallon, thus
[tex]\bf \begin{array}{ccllll}
quarts&days\\
\textendash\textendash\textendash\textendash\textendash\textendash&\textendash\textendash\textendash\textendash\textendash\textendash\\
2.5&1\\
x&75
\end{array}\implies \cfrac{2.5}{x}=\cfrac{1}{75}[/tex]
solve for "x"
that'd give you how many quarts in 75 days, divide it by 4, to get the gallons
