Final answer:
If two angles are supplementary, it does not necessarily mean they are a linear pair. A valid counterexample to the statement is two right angles.
Step-by-step explanation:
Suppose we have two angles that are supplementary, which means they add up to 180 degrees. In a linear pair of angles, the angles must be adjacent and form a straight line, which means they add up to 180 degrees. Therefore, if two angles are supplementary, it does not necessarily mean they are a linear pair.
For example, consider two right angles. Each right angle measures 90 degrees, so when you add them together, they still form a straight line and add up to 180 degrees. However, right angles are not adjacent angles, so they are not a linear pair.
Thus, a valid counterexample to the statement is two right angles.