Let the length be represented by l and the width, w.
The question says that the length is 3 feet longer than the width. This means that
![l=w+3](https://img.qammunity.org/2023/formulas/mathematics/college/cxuzjl3oh330fxq0nucyjgsse11t36jqcy.png)
The perimeter of a rectangle is given as
![2(w+l)=P](https://img.qammunity.org/2023/formulas/mathematics/college/q9ggvw7bgmc5or077ya139ujk5nf9piswo.png)
The perimeter of the sandbox is given as 22 feet.
Substituting the values for the perimeter and the length (w + 3) into the perimeter formula, we have
![2(w+w+3)=22](https://img.qammunity.org/2023/formulas/mathematics/college/vr93q1x5rj6bt7ci0rg8i2ymsd6o7y7yce.png)
Solving, we have
![\begin{gathered} 2(2w+3)=22 \\ 2w+3=(22)/(2) \\ 2w=11-3 \\ 2w=8 \\ w=(8)/(2) \\ w=4 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/cykj7nqyjmvrr2w2eewnhaa7xr8tmicrkg.png)
Now that we have the value for the width, we can calculate the length as
![\begin{gathered} l=w+3 \\ l=4+3 \\ l=7 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/7mm2wgfolmx5uzk9m9pwnb00grtq65f3rp.png)
The length is 7 feet and the width is 4 feet.