Answer
$m \angle X = 100^{\circ}$
Work Step by Step
In congruent polygons, vertices are named in the exact order of their matching vertices.
If $WXYZ$ is congruent to $PQRS$, then vertex $W$ corresponds to vertex $P$, vertex $X$ corresponds to vertex $Q$, vertex $Y$ corresponds to vertex $R$, and vertex $Z$ corresponds to vertex $S$.
Therefore, $\angle X$ is congruent to $\angle Q$. So, $m \angle X$ is equal to $m \angle Q$. If $m \angle Q$ is $100^{\circ}$, then $m \angle X$ is $100^{\circ}$.
