The sum of two adjacent angles can be either complementary or supplementary based on their measures. If two adjacent angles are placed next to each other on a straight line they will add up to 180° because these will be adjacent supplementary angles. If the adjacent angles do not form linear pairs, they will not add up to 180°.

Complementary angles are two angles whose measures add up to 90°. Complementary angles are not necessarily adjacent angles. But every two adjacent angles whose measures add up to 90° are complementary.

Adjacent angles can be a complementary angle or supplementary angle when they share the common vertex and side. If the sum of adjacent angles is equal to 90 degrees, then they are complementary to each other If the sum of adjacent angles is equal to 180 degrees, then they are supplementary to each other

When they are adjacent to each other, you’ll realize that they form a right angle. A right angle measures exactly, so are complementary angles. However, two angles don’t need to be adjacent or have a common side and vertex to be called complementary angles. If their angle measures add up to, they are also complementary.

In the figure given below, ∠COB and ∠AOB are adjacent angles as they have a common vertex "O" and a common arm "OB". They also add up to 90 degrees, that is ∠COB + ∠AOB = 70° + 20° = 90°. Thus, these two angles are adjacent complementary angles.