Given
360 miles on 12 gallons; 270 miles on 9 gallons
Procedure
[tex]\frac{360\text{ miles}}{12\text{ gallons}}=30\text{ miles/gallon}[/tex][tex]\frac{270\text{ miles}}{9\text{ gallons}}=30\text{ miles/gallon}[/tex]
In this case the two fractions have the same ratio. Therefore they are proportional.
