A 50-gon is a polygon that contains 50 sides. Just like all polygons, no matter what the number of sides, the total of all exterior angles of any concave polygon will be 360 degrees.
Providing it's a regular polygon: 360/50 = 7.2 degrees
Now, a 50-gon (the correct term is a pentacontagon, but that takes too long to type) has 50 sides. The equation for the interior angle of a regular polygon (we're talking about a regular 50-gon, right?) is [(n-1)*180]\n where n is the number of sides the polygon has. So in this case, the sum of the interior angles is 8820, and the measure of one angle is 176.4 degrees.