These angles have a common vertex and a common side. The sum of two angles doesn't necessarily have to be 180 degrees for them to be adjacent angles.
When two angles are added and the sum is 180 degrees, they are supplementary angles. The supplement of angle "x" is 180 degrees minus x. Supplementary angles also are adjacent angles.
When two straight lines intersect with each other, four angles are formed. The nonadjacent angles are called vertical angles or vertically opposite angles. The angles adjacent to each other are called supplementary angles. Both of the vertically opposite angles are supplementary to either of the adjacent angles and therefore equal and congruent.
Vertical angles are always equal, and both pairs of vertical angles always add up to exactly 360 degrees.