Answer :
Let's take a look at the situation:
Notice that angles AC and BC lay in the same straight line. Thereby,
[tex]m\angle AC+m\angle BC=180[/tex]Therefore, both angles are supplementary

Let's take a look at the situation:
Notice that angles AC and BC lay in the same straight line. Thereby,
[tex]m\angle AC+m\angle BC=180[/tex]Therefore, both angles are supplementary