Answer:
![2.4\text{ feet}](https://img.qammunity.org/2021/formulas/mathematics/high-school/8sgrdprn0je1jzqstyx6mjqw2ax9vgglq4.png)
Explanation:
A rectangle's perimeter is given by the formula:
![P=2(l+w)](https://img.qammunity.org/2021/formulas/mathematics/high-school/u2zh6atmobu8pylyyhrjk8f41mol6cwppd.png)
A rectangle's area is given by the formula:
![A=lw](https://img.qammunity.org/2021/formulas/mathematics/middle-school/d9mfw1kn202ewxei9fp0lhh3q6jf79i72v.png)
We are given that they have the same numerical value. In other words:
![2(l+w)=lw](https://img.qammunity.org/2021/formulas/mathematics/high-school/3to6wqw8qm0wroukbcbivst1s3spawah4m.png)
And we are also given that the length is 12 feet. So, substitute 12 for l:
![2(12+w)=12w](https://img.qammunity.org/2021/formulas/mathematics/high-school/whqbyaabix0l3te1b2erwv95rjh6rjnsxr.png)
To solve for the width, we just need to solve for w.
On the left, distribute:
![24+2w=12w](https://img.qammunity.org/2021/formulas/mathematics/high-school/aqyu0w2v48mg8ivmvd9nh22p5ax5bl3vhu.png)
Subtract 2w from both sides. The left side cancels:
![24=10w](https://img.qammunity.org/2021/formulas/mathematics/high-school/vy5g25a23qlli6vqbi71uimvr6tpib1jda.png)
Divide both sides by 10. Flip also:
![w=(24)/(10)](https://img.qammunity.org/2021/formulas/mathematics/high-school/2y7f808tibpcr4g6f0sls8cmt9gfgzs1q9.png)
Reduce both layers. Use 2. So:
![w=12/5=2.4](https://img.qammunity.org/2021/formulas/mathematics/high-school/lqkpyyz9vpqxknztyqq6zi7k4c6c7sf2ua.png)
So, the width is 2.4 feet.
And we're done!