<PRE><B>Question 132875</B>
Given:
1800 total miles
51 gallons
25 miles per gallon city
40 miles per gallon highway


The total distance is the sum of the mileage of city and highway.
Let x be the number of gallons used for city driving. If so, then 51-x is the number of gallons used for highway. 

Now setup an equation for the total mileage driven

Thus :
{{{Total = highway + city }}}
{{{1800 = (51-x)40 + x(25) }}}
{{{1800 = 2040 -40x + 25x }}}
{{{-240 = -15x }}}
{{{ 16 = x }}} Thus city driving used 16 gallons. To find the number of city miles, just multiply the number of gallons times the stated city rate of 25. 

Yielding 400

Check your answer using highway milage to ensure the total is correct.
51-16 = 35
35 * 40 = 1400

total is 1400 + 400 = 1800!!</PRE>