Answer:
300 miles
Step-by-step explanation:
Let the gallons of fuel used on highway be X
gallons of fuel used in city be Y
Given that total no of gallons consumed on trip is 14
hence
X + Y = 14 -----------------------equation A
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Given
no. of miles car can drive on highway using 1 gallon of fuel = 30
therefore
no. of miles car can drive on highway using X gallon of fuel = 30X
no. of miles car can drive in city using 1 gallon of fuel = 25
therefore
no. of miles car can drive in city using Y gallon of fuel = 25Y
Given that total miles driven on trip is 400 miles
therefore
30X + 25 Y = 400 ---------------------------------equation B
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now we have two equation
X + Y = 14 -----------------------equation A
Y = 14 - X -----------------------equation C
30X + 25 Y = 400 ---------------------------------equation B
substituting value of Y from equation C in equation B we have
30X + 25 Y = 400
=> 30X + 25 (14 - X) = 400
=>30X + 350 - 25X = 400
=> 5X = 400 - 350 = 50
=> X = 50/5 = 10
Y = 14 - X = 14 - 10 = 4
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now we have to find miles drove on highway
we have defined above
no. of miles car can drive on highway using X gallon of fuel = 30X
where X is no of gallons of fuel used on highway
therefore
no. of miles car can drive on highway using X gallon of fuel = 30*10 = 300
