Question

A boat can teavel 420 miles on 42 gallons of gasoline. How much Gasoline will it need to go 180 miles.

Answer 1

`\bf \begin{array}{ccll} miles&gallons\\ \cline{1-2} 420&42\\ 180&g \end{array}\implies \cfrac{420}{180}=\cfrac{42}{g}\implies \cfrac{7}{3}=\cfrac{42}{g}\implies g=\cfrac{3\cdot 42}{7}\implies g=18`