Answer
64 ft.
Work Step by Step
Define the variables: x=width of the garden; y=length of the garden
Perimeter of the garden: $2y + 2x$
Since the walkway is 8 ft, it's length and width are extended 8 ft from the original garden.
Walkway width (x): $x+16$
Walkway length (y): $y+16$
Formula for perimeter: $2y+2x = P$
Plug in the walkway length and width: (y+16) + (y+16) + (x+16) + (x+16)
This combines to $2y + 2x + 64$
When the perimeter of the garden is subtracted, you receive: $2y + 2x + 64 - (2x + 2y) = 64$
Thus, the difference if 64 ft.
