You need to find the area of the entire circle and subtract off the area of the square.
Area of circle = pi * r^2
r = d/2 = 14/2 = 7 ft
A circle = 3.14159 * 7^2 = 153.94 ft^2
Area of square = s^2
s = 6
A square = 6^2 = 36 ft^2
Subtract to find shaded area
153.94 - 36 = 117.94 ft^2