Let us assume the length of the rectangle = x
Width of the rectangular dog run = 888 feet
Area of the rectangular dog run = 208 square feet
We already know
Area = Length * Width
Length = Area/Width
= 208/888 feet
= 0.23 feet
So the length of the rectangular dog run is 0.23 feet. Since you have commented that you made a mistake in giving the question so the answer will also definitely change but the procedure will remain the same.