30 points if you can help me do all this please

What are the soultion(s) to the quadratic equation 40- x^2=0

1mile equals approximately 1.6 kilometers. which best approximates the number of miles in 6 kilometers?

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?