If Harry drives 15,000 miles in a year, and his car can travel 25 miles on one gallon of gas, then you first need to find out how many gallons of gas he would use in 15,000 miles.
15,000 / 25 = 600
600 gallons of gas in 15,000 miles.
If one gallon of gas releases 20 pounds of Co2, then you need to find out how much Co2 is released by 600 gallons.
600 x 20 = 12,000
His vehicle will add 12,000 pounds of Co2 to the atmosphere.
