Question

which angle number represents an angle vertical to ∠bgc?

Explanation:

Step1: Recall vertical - angle definition

Vertical angles are formed when two lines intersect. They are opposite each other and are congruent.

Step2: Identify intersecting lines

Lines $AB$ and $CD$ intersect at point $G$.

Step3: Find the vertical angle

The angle vertical to $\angle BGC$ is $\angle AGD$. In terms of the numbered angles, $\angle BGC$ and $\angle 2$ are vertical angles.

Answer:

$\angle 2$