The rectangle is given with sides as length (L) and width (W).
If the width is 9 feet greater than its length, that means its width W is equal to 9 + L (9 feet greater than or added to the length).
That means if the length is given as L, then the width would be given as 9 + L
The perimeter of a rectangle is given as
Perimeter = 2 (L +W)
If the perimeter is 86 feet, then we can write
86 = 2 (L + W)
Where L = L and W = 9 + L
86 = 2 (L + 9 + L)
86 = 2 (9 + 2L)
86 = 18 + 4L
**Note that the 2 expands the entire parenthesis**
86 = 18 + 4L
Subtract 18 from both sides of the equation
68 = 4L
Next you divide both sides of the equation by 4 and you have
17 = L
If its length is 17, and the width is 9 feet greater than its length then the width becomes 17 + 9 which equals 26.
Therefore, the width of the rectangle is 26 feet.