Question

details
no additional details were added for this assignment.
$m\angle6 + m\angle5 = 180^{circ}$
$m\angle6 + 120^{circ}=180^{circ}$ substitution property of equality
$m\angle6 = 60^{circ}$ subtraction property of equality
linear pair postulate alternate interior angles theorem substitution property of equality
corresponding angles postulate

Explanation:

Step1: Identify the relationship

The equation $m\angle6 + m\angle5=180^{\circ}$ is based on the fact that $\angle6$ and $\angle5$ form a linear - pair. A linear pair of angles is a pair of adjacent angles whose non - common sides are opposite rays, and by the Linear Pair Postulate, the sum of the measures of angles in a linear pair is $180^{\circ}$.

Answer:

Linear Pair Postulate