Two adjacent, supplementary angles form a straight line
Explanation;
Supplementary angles are those angles whose sum add up to 180 degrees. Thus, two angles are said to be supplementary if their sum adds up to 180 degrees.
Similarly, angles on a straight line add up to 180 degrees, which means they are supplementary angles.
Thus, two adjacent supplementary angles add up to 180 and it means they are on a straight line.
