The delivery person will use 6 gallons of gasoline
The function to determine the number of miles in x hours is:
f(x) = x² + 3x
The number of gallons of gasoline used for driving y miles is:
g(y) = y/18
For a delivery person that works a 9-hour shift:
x = 9
f(9) = 9² + 3(9)
f(9) = 81 + 27
f(9) = 108
That is, the number of miles, y = 108 miles
The number of gallons of gasoline used:
g(y) = y/18
g(108) = 108/18
g(108) = 6
The delivery person will use 6 gallons of gasoline
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