Answer:
Option E:
![12x+28](https://img.qammunity.org/2020/formulas/mathematics/middle-school/mbtsasdb9mqwoopijyoc6zdvoiy53vj3ox.png)
Explanation:
You need to remember that the perimeter of a rectangle can be calculated with the following formula:
![P=2l+2w](https://img.qammunity.org/2020/formulas/mathematics/middle-school/jrrjtqbrnnug86tbamhopeqdpqvldk6qkq.png)
Where "l" is the lenght of the rectangle and "w" is the width of the rectangle.
In this case, you can identify from the figure that:
![l=3x+14\\w=3x](https://img.qammunity.org/2020/formulas/mathematics/middle-school/g009p7lj60l4bjm8qv5260y1x5uefhlbay.png)
So, knonwing this, you can write the following expression to represent the perimeter of the rectangle:
![2(3x+14)+2(3x)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/rk7qoshgvkqe679a3ltpcticea8tjat48r.png)
The final step is to simplify the expression. Then you get:
![=6x+28+6x=12x+28](https://img.qammunity.org/2020/formulas/mathematics/middle-school/6bogco9nz30qdt6plcxtpsoea5mf4q8ahz.png)
This matches with the Option E.