a)
Muscle Fitness has an $80 membership fee, but Muscle Fitness takes $20 off this one-time fee. The one-time fee, therefore, is $60.
Keeping the membership at Muscle Fitness requires that the member pay $15 per month and an additional $5 per month for maintenance, so $20 per month is what is required.
The expression that represents this membership cost is \(20x+60\), and let x represent the number of months.
b)
Tom's brother mentions the competing fitness center, Platinum Gym, but it appears as if we are lacking information in order to make a mathematical judgment.