Answer: Tim has he been a member at 24 Hour Fitness for 4 months.
Explanation:
Let x represent the number of hours for which Tim has been a member at 24 Hour Fitness.
24 Hour Fitness charges $55 for a sign-up fee plus $30 per month to join their gym. This means that the total amount that 24 Hour Fitness charges for x months would be
30x + 55
Tim has paid $175 for his gym membership so far. This means that
30x + 55 = 175
30x = 175 - 55
30x = 120
x = 120/30
x = 4