Average Fuel Economy
Let "x" represent the average fuel usage rate while going up the hill.
On the second run on this same course he reset the "Average Fuel Economy" gauge sooner and drove "y" km. on this level road with a reading of 7 AVG L/100km. He then proceeded up the same hill, but this time the reading at the top of the hill was only 11 AVG L/100km.
State the sum x + y.