Final answer:
The measure of the supplementary angle to an angle of 99 degrees is 81 degrees. Supplementary angles add up to 180 degrees.
Step-by-step explanation:
The measure of an angle is 99 degrees. To find the measure of its supplementary angle, we need to know that the sum of the measures of supplementary angles is always 180 degrees. Therefore, we subtract the given angle from 180 degrees to find the measure of the supplementary angle.
The calculation would be: 180 degrees - 99 degrees = 81 degrees. So, the measure of the supplementary angle is 81 degrees.