Answer:
Each exterior angle measures 360/19 degrees, approximately 18.9 degrees.
Explanation:
Start at one vertex of the polygon and go clockwise. When you reach the next vertex, you change direction. At each vertex you change direction by the same angle. When you are back to the first vertex, and start along the first side, you have completed a full 360 degrees clockwise. Since there are 19 sides and vertices, you must have turned 360/19 degrees at each vertex.