Answer: Our required equation to find the total cost of his monthly membership to the gym would be

Explanation:
Let C be the total cost for your monthly membership.
Let p be the number of times you used the pool in one month.
Cost of every time he want to use the pool = $2
Monthly fee = $50
According to question, it becomes,

Hence, our required equation to find the total cost of his monthly membership to the gym would be
