Solution:
To solve for the missing side length, we can use the property that corresponding sides of similar triangles are proportional.The corresponding sides of the triangles are in proportion, so we can set up the following equation:\[ \frac{x}{8} = \frac{8}{16} \]Now solve for $$ x $$:\[ x = \frac{8 \times 8}{16} \]\[ x = \frac{64}{16} \]\[ x = 4 \]Therefore, the missing side length $$ x $$ is 4 units.