Here is the pool only, which is 46 feet across.



So it has a radius of half that, or 23 feet:



The area of the pool is given by the formula



It has a walk around it which is 4 feet wide.



If we take out the inner circle, like this:



we see that the outer circle, which includes both the
pool and the walk, has a radius of 
 or  feet.



The area of the outer circle which includes
the pool and the walk is given by the formula:



Going back to the original picture:



AREA OF WALK = AREA OF OUTER CIRCLE - AREA OF INNER CIRCLE =



 square feet.

Edwin