x - the unit of the length
11 : 1 - the ratio of the length to the width
11x - the length1x - the width
168 ft. - the perimeter of a rectangle
2 · 1x + 2 · 11x - the perimeter of a rectangle
2x + 22x = 168
24x = 168 |:24
x = 7
Answer: The width of the rectangle is equal 7 ft.