Please Answer this question I am very confused

Cara earns a base pay of $1800 per month at a car dealership plus a commission of 6% of her sales. what are caras total earning in a month in which she sells $40000 worth of merchandise

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?

The radius of a sphere is 3 inches. which represents the volume of the sphere?