The number of miles he drove for a cost of $30.50 is 275 miles.
Using linear equation,
y = mx + b
where
Therefore,
9 cents = $0.09
y = 35.50 + 0.09x
where
x = number of miles drove
y = total cost
Therefore,
60.25 = 35.50 + 0.09x
60.25 - 35.50 = 0.09x
24.75 = 0.09x
x = 24.75 / 0.09
x = 275 miles
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