Suppose you drive an average of....HELP

Quote:

Suppose you drive an average of 18000 km/year. With our present car, you can drive 10km per liter of a fuel. You are thinking of buying a new car that you could drive x km farther per liter of fuel. Fuel currently costs $0.68/Liter. If the new car would save $244.80 in yearly fuel costs, find the number of kilometers you could drive the new car per liter of fuel.

Well this is going to be on a test tommorow, and I just can't figure it out! I found out the spendings per year on fuel and stuff but just cant make the relation to the equation. Also the unit we are during is Rational Variable Expressions.

Much thanks in advance.