I'm assuming you're trying to find out how much you'll spend annually on gas: first you would divide the total miles driven in a year (13,000) by your car's mpg (26) giving you a quotient of 500 (the amount of times you'll have to fill up your tank) from here you will need to multiply 500 times the cost of gas ($3.60) giving you a product of $1,800 spent on gas annually.
