The segments AB and CD intersect at point O, which is the middle of each of them, prove that AOC is equal to the angle BOD

The segments AB and CD intersect at point O, which is the middle of each of them, prove that AOC is equal to the angle BOD. Find OAC if ODB is 20 degrees, and AOC is 115 degrees

If we draw these intersecting segments, then we get that the angle AOC and BOD are vertical, which means that they are equal.
The AOC and BOD triangles are equal in the first attribute (two sides, the angle between them). This means that their respective angles are equal. We get that the angle ОВD = angle ОАС and = 20 °.