The cost to rent a bike at the beach is $6.75 an hour plus an insurance fee of $15. Marcia spent $48.75 when renting a bike on a recent trip to the beach. For how many hours did Marcia rent the bike?
Let x be the number of hours renting the bike.
Marcia paid 6.75x + 15 = $48.75
Subtracting 15 from both sides:
6.75x = 33.75 dollars
To get the value of x divide both sides by $6.75
x = <<5=5>>5
Marcia rented the bike for 5 hours. Answer: \boxed{5}.