Final answer:
The measure of the angle is 100° and the measure of its supplementary angle is 80°.
Step-by-step explanation:
Let's represent the angle as x and its supplementary angle as 180 - x.
According to the given information, x = (180 - x) + 20.
Simplifying the equation, we get x = 200 - x.
Combining like terms, we have 2x = 200.
Dividing both sides by 2, we find x = 100.
Therefore, the angle measures 100° and its supplementary angle measures 80°.