
Jonathan W. answered 11/21/14
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Patient and Knowledgeable Berkeley Grad for Math and Science Tutoring
If a and b are supplementary, then a + b = 180°, so b = 180° - a.
Now you have to decide whether you're naming the angles so that a > 180° - a or vice versa.
If a > 180° - a, then a - (180° - a) = 36°. Solve for a, and you're done.
(Otherwise, (180° - a) - a = 36°. Solve for a, and subtract from 180°.)