Question

look at this diagram: if df and gi are parallel lines and m∠ihe = 129°, what is m∠deh?

Explanation:

Step1: Identify angle - relationship

$\angle IHE$ and $\angle DEH$ are vertical angles.

Step2: Apply vertical - angle property

Vertical angles are congruent. So, $m\angle DEH=m\angle IHE$.

Answer:

$129^{\circ}$