Given that the total cost of Anfa's trip to the dentist was $ 628.35, and she paid a flat fee of $ 89.95 which included the checkup: cleaning and then had 4 cavities filled, each of which cost the same amount, to determine which shows the correct equation and value of x, the cost of each cavity filling, the following calculation must be performed:
(628.35 - 89.95) / 4 = X
538.4 / 4 = X
134.6 = X
Therefore, the cost of each cavity filling was $ 134.60.