Let h be the amount of hours that the life jackets and the paddle boat are used.
Since the two friends must pay $20 for every hour, then the amount charged for h hours is:
On the other hand, they must pay a onetime fee of $7 additional to the cost for using the equipment for h hours. Then, add 7 to the expression 20h to find the total cost:
Therefore, the expression that represents the total cost to rent the life jackets and paddle boat for h hours, is: