Question

in the figure, m∠7 = 100°. find the measure of ∠2.

Explanation:

Step1: Identify angle - pair relationship

$\angle7$ and $\angle5$ are vertical angles. Vertical angles are congruent. So $m\angle5=m\angle7 = 100^{\circ}$.

Step2: Identify another angle - pair relationship

$\angle5$ and $\angle2$ are corresponding angles. When two parallel lines are cut by a transversal, corresponding angles are congruent. So $m\angle2=m\angle5$.

Answer:

$100^{\circ}$