Answer
$B$
Work Step by Step
Vertical angles are congruent. If they are also supplementary, then the sum of the two angles is $180^{\circ}$. The two vertical angles can be represented by the expression $2x$, where $x$ is the measure of one of the vertical angles. Let's set up the equation:
$2x = 180$
Divide each side by $2$ to solve for $x$:
$x = 90$
This answer corresponds to option $B$.
