David ran the yard dash in 7.2 seconds and won the event justin came in second with a time of 8.1 seconds how much better was davids time than justins

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?