Question

what is ( mangle 1 )?
( mangle 1 = square^circ )

Explanation:

Step1: Identify interior angles

The triangle has interior angles $107^\circ$ and $31^\circ$.

Step2: Use exterior angle theorem

The measure of an exterior angle of a triangle equals the sum of the measures of the two non-adjacent interior angles.
$m\angle1 = 107^\circ + 31^\circ$

Step3: Calculate the sum

$m\angle1 = 138^\circ$

Answer:

$138$