Question 1152022
R, fuel efficiency
V, volume of fuel, gallons
D, distance in miles
{{{R=V/D}}}


Question asks for how many gallons used in the city.  Let this quantity be v.

<pre>
                  FUEL EFFC      VOL        DISTANCE
CITY              12.8            v         12.8v
HIGHWAY           21.6           20-v       21.6(20-v)
TOTAL                            20        308.8 
</pre>
{{{12.8v+21.6(20-v)=308.8}}}
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{{{steps}}}
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{{{highlight(v=14)}}}