Question

1. 156° ? 20° 35°

Explanation:

Step1: Find adjacent angle

The 156° angle and its adjacent angle on the straight line are supplementary.
$180^\circ - 156^\circ = 24^\circ$

Step2: Calculate unknown angle

Sum of angles in a triangle is 180°.
$180^\circ - 20^\circ - 35^\circ - 24^\circ = 101^\circ$

Answer:

101°