The truth value of this statement depends on the position of the angles.
Adjacent Supplementary Angles
The sum of the measure of supplementary angles is 180. If the angles are adjacent, then together they form an angle of measure 180 — a straight angle. Two angles that form a straight angle are a linear pair, so it is possible that two supplementary angles form a linear pair.
Nonadjacent Supplementary Angles
Angles in a linear pair are adjacent, so if the angles are not adjacent, then they cannot form a linear pair.
Conclusion
Sometimes two supplementary angles form a linear pair, but sometimes they do not.
