Lee filled up his gas tank before starting a road trip. if he used 5.8 gallons two hours into the trip, and has 12.4 gallons remaining, how many gallons did he start with?

The answer would be 18.2 gallons because they used up 5.8 gallons, they still have 12.4 gallons that they did not use and in order to get the original amount of gas they had before the trip, you would add up 12.4 and 5.8 to get the Original amount. Hope this helps.