1st circle ⟶ with radius 3

2nd circle ⟶ with radius 7

3rd circle ⟶ with radius 9

Area of 1st circle = (3)^{2} = 9π

Area of 2nd circle= (7)^{2} = 49π

Area of 3rd circle = (9)^{2} = 81π

Area of shaded region = Area of 2nd circle – area of 1st circle

= 49π – 9π

= 40π

Probability that will land on the shaded region = (area of shaded region)/(area of 3rd circle) =40π/81π = 40/81