Given the following diagram, find the missing measure.
given:
m∠p = 40°, m∠1 =
40
50
90
130

The answer is 130 degrees and this is why: 

The sum of the interior measures of all triangle is equal to 180 degrees. Since side PM is perpendicular to side MO, it forms a right angle, or 90 degree angle, so that gives you the measure of one of the interior angles. The problem also gives you the measure of another interior angle, P, as 40.

So you add the two angle measures to get 130 degrees. Subtract that number from 180 to get the measure of angle 2, which is 50. Because angle 2 and 1 are supplementary, their angles add up to 180. Subtract the measure of angle 2, 50, from 180 to get the measure of angle 1, which is 130. 

Hope this helps!