Given in the question:
a.) The perimeter of the shape is 34 units.
b.) The width of the shape is 8 units.
To be able to determine the measure of the missing side, let's first recall what is the formula in getting the perimeter of the shape which is a rectangle.
![\text{ Perimeter = 2W + 2L}](https://img.qammunity.org/2023/formulas/mathematics/college/el590hde3xzw48mrui6h1o9xixoytqy9zd.png)
Let's use the formula in getting the measure of the missing side since we know that the total perimeter is 34 units and its width is 8 units.
![\text{ Perimeter = 2W + 2L}](https://img.qammunity.org/2023/formulas/mathematics/college/el590hde3xzw48mrui6h1o9xixoytqy9zd.png)
![\text{ 34 = 2(8) + 2L}](https://img.qammunity.org/2023/formulas/mathematics/college/gwy2y25mhfovixpp0ysx0jsqv50n416has.png)
![\text{ 34 = 16 + 2L}](https://img.qammunity.org/2023/formulas/mathematics/college/69h35t0gxdqf5a3xb86dmuvp77tf7gbz33.png)
![\text{ 2L = 34 - 16 = 18}](https://img.qammunity.org/2023/formulas/mathematics/college/i242ezp37a55p73wcwrxvpkz5vf6hpvoim.png)
![\text{ }\frac{\text{2L}}{2}\text{ = }\frac{\text{18}}{2}](https://img.qammunity.org/2023/formulas/mathematics/college/i77yfluv827872px3ny1nb8hjwc64e9856.png)
![\text{ L = 9}](https://img.qammunity.org/2023/formulas/mathematics/college/1oiahmkd5c9thulmaui91krk2cvxustvct.png)
Therefore, the measure of the missing side L is 9 units.