Given:
We already know that the sum of two supplementary angles must be equivalent to 180°. Therefore, we obtain the following equation:
When we plug the value of "the first supplementary angle", we get:
When simplified, we get:
Therefore, the measure of the second supplementary angle is 103°. Now, let's substitute the measure of the second supplementary angle into the given equation to determine the measure of the first supplementary angle.
Therefore, the measure of the first supplementary angle is 77°.