Given :
A rectangle with a length of 3 x and height of x. If Kyle uses 18 feet of wood to make the frame.
To Find :
The length of the frame.
Solution :
We know, perimeter of the rectangle is given by :
![P=2(l+b)\\\\P=2(3x+x)\\\\P=8x](https://img.qammunity.org/2021/formulas/mathematics/high-school/1wgts15cz2a7ttg9f94mu9osrw4mv62497.png)
Now, it is given that 18 feet of wood is used.
So,
![8x=18\\\\x = 2.25\ feet](https://img.qammunity.org/2021/formulas/mathematics/high-school/gsy9022araw8kjl11a6d9ojpe3xdvg4le6.png)
Therefore, length of frame is given by 3x = 6.75 feet.
Hence, this is the required solution.