we know there are 4 quarts in a gallon, so how many quarts in 2.5 gallons anyway?
[tex]\bf \begin{array}{ccll}
quarts&gallons\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
4&1\\
x&2.5
\end{array}\implies \cfrac{4}{x}=\cfrac{1}{2.5}\implies \cfrac{4\cdot 2.5}{1}=x[/tex]
