Mr. Shindler begins traveling east on Interstate 90 from Spokane with a full tank of gasoline. His car has a 15-gallon gas tank and gets 30 miles per gallon during highway travel.

Let m = the number of miles Mr. Shindler has driven

Let g = the number of gallons of gas remaining in his tank

Select and justify in the answer box which equation describes the relationship between the number of miles Mr. Shindler has traveled and the number of gallons remaining in his gas tank.