Beth and darcy are each driving a car. they start at the same location and will be driving the same route. beth's car has a gas tank that can hold 15 gallons of gas. her car uses 1 30 of a gallon of gas per mile driven. darcy's car has a gas tank that can hold 16 gallons of gas. his car uses 1 25 of a gallon of gas per mile driven. both cars start with full tanks of gas. after how many miles will both cars have the same number of gallons of gas remaining in their gas tanks?