Answer:
1. given
2. def of supplementary angles
3. substitution property of equality
4. subtraction property of equality
5. if two angles have the same measure they are congruent
Explanation:
1. the first is always a given
2. if they are supplementary they are always 180 degrees
3. you substitute the 180 for the other equation because they are both equal
4. you subtract angle two from both
5. if two are equal they are congruent, which means the same measure.