Given:
Width of the rectangular yard = x feet
Length of the rectangular yard = x+4 feet
Perimeter of the rectangular yard is:
![P=4x+8](https://img.qammunity.org/2022/formulas/mathematics/college/88aki1ywah7209er053cwfi3964aat7hg2.png)
Perimeter of the yard = 84 feet
To find:
The length of the rectangular yard.
Solution:
Perimeter of the yard is 84 feet.
![4x+8=84](https://img.qammunity.org/2022/formulas/mathematics/college/gz93qxm6z07wntohb5jp17y45a30m1j4wm.png)
![4x=84-8](https://img.qammunity.org/2022/formulas/mathematics/college/pibkx9sxr0lt713f7bgt49hqh7vdydiin9.png)
![4x=76](https://img.qammunity.org/2022/formulas/mathematics/college/6iha7clpz94oxtqze6ftac5hlad08bmbgx.png)
Divide both sides by 4.
![x=(76)/(4)](https://img.qammunity.org/2022/formulas/mathematics/college/4q77lawltsjpuk5vbz26rsniflrkxy2k7w.png)
![x=19](https://img.qammunity.org/2022/formulas/mathematics/high-school/1z2y4r4rofi0jwbg28xsqrihd6zpsamxlt.png)
So, the width of the rectangular yard is 19 feet.
Length =
![19+4](https://img.qammunity.org/2022/formulas/mathematics/college/k6c0ls37sriv3zrj61c4lkl9ad3q36052p.png)
Length =
![23](https://img.qammunity.org/2022/formulas/mathematics/high-school/x9eemwj7li8g7e3r4kk7tz9yvov5mcw8fl.png)
The length of the rectangular field is 23 feet.
Therefore, the correct option is B.