We subtract the area of the fountain (a(f)) from the total area of the fountain + walk (a(t)), to find the area of the walk (a(w))
diameter of fountain = 10 so r = 5
a(f) = pi*r^2 = pi*25 = 78.5
r of fountain + walk = 5 + 3 = 8
a(t) = pi*r^2 = pi*64 = 200.96
a(w) = a(t) - a(f) = 200.96 - 78.5 = 122.46 square feet
