Question 1052481
The problem description is not complete, so this is the biggest difficulty.


Two different cars, each with its own fuel efficiency ( a uniform rate for each car), and different quantity of gallons used for each car to make a total fuel quantity in gallons.  Nothing described about distance!


Tabulating the description shows you:
<pre>
               FUEL EFFICIENCY (miles/gal)    VOLUME (gal)   DISTANCE (miles)
CAR ONE                16                        x             (  )
CAR TWO                22                        y             (  )
Total/s                                         20             (  )
</pre>

R*V=D shows a basic rule to relate fuel efficiency, fuel volume, and distance.


The only meaningful equation you can make here is {{{x+y=20}}}.


Upon further thinking, the fuel efficiency data are not important.  This is not really a uniform rates problem.  What you are really looking for is x+y<=20, and both x and y must be restricted to between 0 and 20.  Negative numbers for x or y not allowed.