ANSWER
72 square feet
Step-by-step explanation
The perimeter of a rectangle is given by:
P= 2l+2w
It was given that, the perimeter of the rectangular mat, is 36 feet.
36= 2l+2w
Divide through by 2.
![18 = l + w...(1)](https://img.qammunity.org/2020/formulas/mathematics/high-school/9xzq1diq67vs4jmgpqfq2djw8zqk8qf7sz.png)
It was given also that, the length of the mat is twice its width.
This implies that,
![l = 2w ...(2)](https://img.qammunity.org/2020/formulas/mathematics/high-school/vqhasbrzfyeehj9fuasu1g1rlvf255vid7.png)
Put equation (2) into equation (1) to get,
![18 = 2w + w](https://img.qammunity.org/2020/formulas/mathematics/high-school/djll4zmxamq6dtedaxlsxmqcyz6o1kvsu8.png)
![18 = 3w](https://img.qammunity.org/2020/formulas/mathematics/high-school/3qpfct4aoa52wefk8qpj6lnfc93z374pem.png)
![w = 6 \: ft](https://img.qammunity.org/2020/formulas/mathematics/high-school/yob9pf49qzeu07msxqmq1zzga4s2gwjy57.png)
This means that the length is 12 ft.
The area of the rectangular mat is
![A = l * w](https://img.qammunity.org/2020/formulas/mathematics/high-school/ujm4yzb89s4l45r5ylt38sd45qcuv0aegr.png)
![A = 6 * 12 = 72 {ft}^(2)](https://img.qammunity.org/2020/formulas/mathematics/high-school/2dtyfgcodt381b9pcqsxmae3xmed6qgeim.png)