the vista marina rents boats for $25 per hour in addition to the rental fee there is a $12 charge for fuel is the number of hours you can rent the boat proportional to the total cost
$12 charge for fuel
x quantity of hours
($12)+[($25/hour)(x hours)] = (total cost)/hour
This is the relationship between total cost and quantity of hours.
Before making any calculations, the first priority is to cancel units. If your units are not aligned, you have the wrong equation.
In the numerator, the unit hours appears as both a multiplier and divider within the bracketed equation...
The units which remain are $/hour, or, dollars/hour. This, I think, is the results you are looking for.