Final answer:
Daniel used 23.5 gallons of gas on his trip.
Step-by-step explanation:
To find out how much gas Daniel used on his trip, we need to calculate the difference between the initial amount of gas and the amount left at the end.
Starting with 12.8 gallons and filling the tank with 14.4 gallons, the total amount of gas available for the trip is 12.8 + 14.4 = 27.2 gallons.
Then, to find out how much gas Daniel used, we subtract the amount left at the end from the total amount available: 27.2 - 3.7 = 23.5 gallons.
Therefore, Daniel used 23.5 gallons of gas on his trip.