Question

what is $m\angle 1$?
image of a triangle with angles 81° and 62°, and angle 1 adjacent to one side extended
$m\angle 1 = \square^\circ$

Explanation:

Step1: Find triangle's top interior angle

First, calculate the unknown interior angle of the triangle using the fact that the sum of interior angles in a triangle is $180^\circ$.
$180^\circ - 81^\circ - 62^\circ = 37^\circ$

Step2: Calculate supplementary angle $\angle1$

$\angle1$ and the top interior angle are supplementary (they form a straight line, sum to $180^\circ$).
$180^\circ - 37^\circ = 143^\circ$

Answer:

$143$