Taking into account that the amount of gasoline used is directly variable to the distance traveled in a car, to find the constant of variation in miles per gallon you need to have an end value that will give you how many miles can be travelled with one gallon. The information we have tells us that 520 miles use up 26 gallons, so 520 miles per 26 gallons. To find how many miles are done with only one gallon divide the 520 miles by the 26 gallons. 520/26 =20miles per gallon 20mpg is the constant of variation, which means that the car uses one gallon in 20 miles of travelling, and will use x gallons in 20 times x miles.
