Find m< 1
a: 69
b: 71
c: 86
d: 111

The correct answer is:  [A]:  "69° " .

     m∠1 = 69° .

Explanation:


180 - (39 + 30) = 180 - 69 = 111.  This is the measurement of the third angle in the triangle.  Note that all angles in a triangle add up to 180° .  All triangles have 3 (three) sides and 3 (three) angles.

To find m∠1 :

The only single angle that exists that is supplementary to ∠1 is 69.

So:   m∠1 = 180 - 111 = 69 .  (Note:  since all angles on a straight line are supplementary angles;  and supplementary angles add up to 180° .

The answer is:  69° .

      m∠1 = 69° .