Its math but please help me out whats x !

Can someone show me the steps to solve the problem?

If x = 12 and y = 3, what is the value of x - y 2? 81 6 3 18

Acircular city park has a sidewalk directly through the middle that is 111 - feet long. if each bag of fertilizer covers 50 square feet, then determine how many bags of fertilizers the parks and recreation department needs to use to cover the circular park. ignore all the sidewalks around and through the park.