How to solve linear pair problems: example and its solution.
A linear pair are angles
whose sum of the adjacent angle's measures is 180.
They have a common side
and a common vertex (red point).
These two angles are a linear pair.
So (13x + 1) + (7x + 9) = 180.
The differece between a linear pair
and supplementary angles is that
supplementary angles don't have to be adjacent.