Answer:
The inequality is 
The greatest length of time Jeremy can rent the jet ski is 5 and Jeremy can rent maximum of 135 minutes.
Step-by-step explanation:
Given: Cost of first hour rent of jet ski is $55
Cost of each additional 15 minutes of jet ski is $10
Jeremy can spend no more than $105
Assuming the number of additional 15-minutes increment be "x"
Jeremy´s total spending would be first hour rental fees and additional charges for each 15-minutes of jet ski.
Lets put up an expression for total spending of Jeremy.

We also know that Jeremy can not spend more than $105
∴ Putting up the total spending of Jeremy in an inequality.

Now solving the inequality to find the greatest number of time Jeremy can rent the jet ski,
⇒ 
Subtracting both side by 55
⇒ 
Dividing both side by 10
⇒
∴ 
Therefore, Jeremy can rent for 
Jeremy can rent maximum of 135 minutes.