Question

Royston’s car had gallons of gas at the start of the trip. During the trip, he stopped at a gas station and refueled the car with gallons. If the car consumed gallons of gas during the trip, there are still
gallons of gas remaining in the tank.

Answer 1

there are quantities missing in the blanks, but the general idea:

gallons left = (gallons at the start) + (amount refilled) - (amount consumed)