In the problem, the length is being compared to the width. So, let x be the width of the rectangle.
width = x
Then, express in math form the condition "the length is 4 ft longer than the width".
length = x + 4
To set-up the equation, apply the formula of perimeter of rectangle.
`P = 2 * (L + W)`
where L is the length and W is the width.
Plugging in the length and width of the given rectangle, the formula becomes:
`P = 2((x+4)+x)`
Also, plug-in the given perimeter P=40.
Hence, the equation is:
Simplifying the right side, it becomes:
Isolating the x result in:
So, the width is 8. And, its length is:
length` =x + 4 = 8 + 4 =12`
Therefore, the rectangle has a length of 12 feet and a width of 8 feet.