Question

If the opposite interior angles of an exterior angle of measure $123°$ is $x$ and $x+3$, then $x$=

• A. 40°
• B. 60°
• C. 80°

Answer 1

The correct option is B 60°

By exterior angle property of a triangle, we must have,
$\angle ABD=\angle A+\angle C$
i.e., $x+(x+3)={123}^{\circ }$
$⟹2x={120}^{\circ }$
$⟹x={60}^{\circ }$