Question

calculate m∠def.

Explanation:

Step1: Identify the angle type

$\angle DEF$ is a straight - line angle.

Step2: Use the straight - line angle property

A straight - line angle measures $180^{\circ}$. But looking at the given figure, $\angle DEF$ is the $120^{\circ}$ angle as per the angle markings in the diagram.

Answer:

$120^{\circ}$