What is the mean absolute deviation of 35 38 41 35 36 55

Based on what i know about mean, this doesn't add up.

What is the solution to the equation? k/6.4=8.7 2.3 5.568 15.1 55.68

The total cost of anja’s trip to the dentist was $628.35. she paid a flat fee of $89.95 which included the checkup and cleaning and then had 4 cavities filled, each of which cost the same amount. which shows the correct equation and value of x, the cost of each cavity filling?