The area of the walkway is 198 m^2.

The formula for the area of the walkway is the area of the circle at the outside of the walkway, minus the area of the circle at the inside of the walkway.

A = Π Ro^2 - Π Ri^2

We also know from the width of the walkway that the outer radius is 3 m larger than the inner radius.

Ro = Ri + 3

We can write...

A = Π (Ro^2 - Ri^2) = Π ((Ri+ 3)^2 - Ri^2)

A = 198 m^2 =  Π (Ri^2 + 6 Ri + 9 - Ri^2) = Π (6 Ri + 9)

Ri =( A/Π - 9 ) /6  = 9.00 m

The inner radius, which is also the radius of the pool, is 9 meters.