The measure of an angle is 159

degrees.

What is the measure of its

supplementary angle?

21°

Step-by-step explanation:

Supplementary is defined as two angles whose sum is 180. These angles must therefore be on a straight line cut by a transversal and must be less than 180 by themselves.

If one angle is 159, then we can simply subtract it from 180 to get the other angle.

A more algebraic way is to set up the equation, 159 + x = 180. Subtract 159 from 180 to find x.