Answer:
The width and the length of the pool are 12 ft and 24 ft respectively.
Step-by-step explanation:
The length (L) of the rectangular swimming pool is twice its wide (W):

Also, the area of the walkway of 2 feet wide is 448:

Where 1 is for the swimming pool (lower rectangle) and 2 is for the walkway more the pool (bigger rectangle).
The total area is related to the pool area and the walkway area as follows:
(1)
The area of the pool is given by:
(2)
And the area of the walkway is:
(3)
Where the length of the bigger rectangle is related to the lower rectangle as follows:
(4)
By entering equations (4), (3), and (2) into equation (1) we have:


By solving the above quadratic equation we have:
W₁ = 12 ft
Hence, the width of the pool is 12 feet, and the length is:

Therefore, the width and the length of the pool are 12 ft and 24 ft respectively.
I hope it helps you!