## Elementary Algebra

Let x represent the amount of gas the car will use on a 615-mile trip. Now, let’s set up a proportion in which one ratio compares the amount of fuel used and the other ratio compares the corresponding distances traveled. $\frac{18}{x}$ = $\frac{369}{615}$ To solve this equation, we equate the cross products. 18 $\times$ 615 = x $\times$ 369 11070 = 369x Divide both sides by 369. 30 = x The car will use 30 gallons of gas on a 615-mile trip.