Question

what is $m\angle 1$?
$m\angle 1 = \square ^\circ$

Explanation:

Step1: Find triangle's third interior angle

First, calculate the unknown interior angle of the triangle using the angle sum property (sum of triangle angles = $180^\circ$).
$\text{Third interior angle} = 180^\circ - 103^\circ - 38^\circ = 39^\circ$

Step2: Relate to exterior angle $\angle 1$

$\angle 1$ and the third interior angle are supplementary (form a straight line, sum to $180^\circ$).
$m\angle 1 = 180^\circ - 39^\circ$

Answer:

$141^\circ$