R, fuel efficiency
V, volume of fuel
D, distance
RV=D
A few different questions can be answered from the analysis of the description.
Give a variable to something.
FUEL EFFIC VOLUME MILES
FirstCar 20
SecondCar 25
TOTALS 45 1050
FUEL EFFIC VOLUME MILES
FirstCar 20 v 20v
SecondCar 25 45-v 25(45-v)
TOTALS 45 1050
You can solve this equation for v, volume of fuel for first car; and then evaluate volume of fuel for second car, and each of the distance for these two cars.