Assumed your shaded part is between the big and the small circle.
Area of the big circle = [tex] \pi r^{2} [/tex] = 3.142 x 5 x 5 = 78.66
Area of the small circle = [tex] \pi r^{2} [/tex] = 3.142 x 3 x 3 = 28.278
Area of the shaded part = 78.66 - 28.278 = 50.6 square units
