Question

A boat can travel 315 miles on 63 gallons of gasoline. How much gasoline will it need to go 5 miles?

Answer 1

$\begin{array}{ccll} miles&\stackrel{gasoline}{gallons}\\ \cline{1-2} 315 & 63\\ 5& x \end{array} \implies \cfrac{315}{5}~~=~~\cfrac{63}{x} \\\\\\ 63=\cfrac{63}{x}\implies 63x=63\implies x=\cfrac{63}{63}\implies x=1$