Answer: you can rent the kayak for 5.3 hours
Explanation:
Total amount of money that you have to spend at the beach is 50.
A kayak cost 5 per hour to rent. This means that if you rent the Kayak for X hours, the amount that you will spend would be 5×x = 5x. I buy lunch for 8.50. I want to save 15 for food later. This means that total amount of money spent is the sum of money spent in renting the kayak and buying of lunch.
Total amount spent = 5x + 8.50
Total amount spent + Total amount that you want to save = Total amount of money that you have to spend at the beach. Therefore
5x + 8.50 + 15 = 50 - 15 - 8.5 = 26.5
x = 26.5/5 = 5.3