Your car's fuel efficiency is e = 26 miles per gallon. The fuel pump pulls fuel from the tank at the same speed vat which the car itself moves (so if the car is moving 1 mile per hour, the fuel moves through the pump at 1 miles per hour). The fuel pump pulls fuel at speed v through a hose with cross-sectional area A.
What is the cross-sectional area of the hose in square inches? What is it in square millimeters? (1 gallon =231 in3. You need to find the volume of fuel pumped per time in terms of v and A Fuel efficiency is distance traveled per fuel pumped, which is equal to speed v divided by fuel pumped per time. The time dependence cancels out. Fuel efficiency has units distance per volume.)