What is the starting mileage? : 12657
The ending mileage is? : 13513
The starting gallon of gas in the tank is? : 20
The ending gallon of gas in the tank is? : 4
The miles traveld is : 856.0
The ending gas usage is : 16.0
The Miles Per Gallons is : 5,350% gallons
The travel cost of gas will be : $45.60
The car MPG rating is : Amazing!
Do you want to continue? (Yes/No):
Well, we could point out that the unit that is produced by dividing unit mile by unit gallon is mile/gallon, not some percentage of a gallon. The output is thus strange, no matter what the values are.
Edit: We probably do guess what you do wrong (without seeing your code) because we are(?) psychics. Can you read the explanation (without us writing it)?