To find the measure of angle B when angles A and B are supplementary, follow these steps:
1. Understand the concept of supplementary angles: Two angles are supplementary if the sum of their measures is 180°.
2. Identify the given information: In this case, you are given that angle A measures 80°.
3. Set up the equation: Since the sum of the measures of supplementary angles is 180°, you can write the equation:
\(\[
\text{measure of angle A} + \text{measure of angle B} = 180°
\]\)
4. Substitute the given measure of angle A into the equation:
\(\[
80° + \text{measure of angle B} = 180°
\]\)
5. Solve for the measure of angle B: Isolate the measure of angle B by subtracting 80° from both sides of the equation:
\(\[
\text{measure of angle B} = 180° - 80°
\]\)
\(\[
\text{measure of angle B} = 100°
\]\)
Therefore, the measure of angle B is 100°.
