I'm going to go out on a limb here and guess that you are looking for the answer to the measure of arc DAB, since we already know that angle DAB is 78. Angle DAB is an inscribed angle. That inscribed angle intercepts arc DCB, and the theorem for that is that an inscribed angle is half the measure of the arc it intercepts. That means that arc DCB measures twice 78, so arc DCB measures 156 degrees. Since the measure around the outside of any circle is 360 degrees, arc DAB is 360 - 156 which is 204 degrees. If this is not what you are looking for, sorry and be more specific next time.
