SOLUTION: Dawn's SUV gets 16 miles per gallon(mpg) in city driving and 24 mpg in highway driving. The SUV is driven 390 miles on 18 gallons of gasoline. How many miles were driven in the cit

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Question 177207: Dawn's SUV gets 16 miles per gallon(mpg) in city driving and 24 mpg in highway driving. The SUV is driven 390 miles on 18 gallons of gasoline. How many miles were driven in the city and how many were driven on the highway.
Answer by Mathtut(3670) About Me  (Show Source):
You can put this solution on YOUR website!
lets call number of gallons used in the city and highway x and y respectively
:
x+y=18.........eq 1
16x+24y=390....eq 2
:
rewrite eq 1 to x=18-y and plug that value into eq 2
:
16(18-y)+24y=390
:
288-16y+24y=390
:
8y=102
:
y=12.75gallons used highway
:
x=18-y=5.25%29gallons used city
:
16(5.25)=84 miles driven in city
:
24(12.75)=306 miles driven on highway