Question

find the measure of the missing angles.

Explanation:

Step1: Use vertical - angle property

Vertical angles are equal. The angle opposite the $21^{\circ}$ angle is also $21^{\circ}$, so $b = 21^{\circ}$.

Step2: Use linear - pair property

The sum of angles in a linear pair is $180^{\circ}$. Angle $c$ and the $21^{\circ}$ angle form a linear pair. So $c=180^{\circ}- 21^{\circ}=159^{\circ}$.

Answer:

$b = 21^{\circ}$, $c = 159^{\circ}$