Calculate the perimeter of the rectilinear polygon shown.

Here are the perimeters for shapes 8, 9, and 10.

8.

Step 1: Identify all side lengths of the rectilinear polygon.
The horizontal sides are $12 \text{ cm}$ (top), $2 \text{ cm}$ (bottom left), $6 \text{ cm}$ (inner bottom), and $2 \text{ cm}$ (bottom right).
The vertical sides are $5 \text{ cm}$ (left outer) and $5 \text{ cm}$ (right outer).
For a rectilinear shape, the sum of all vertical segments going up must equal the sum of all vertical segments going down. Similarly for horizontal segments.
The sum of the outer vertical segments is $5 cm + 5