As the picture below shows, an arc is a part or a portion of a circle.
An intercepted arc is the arc that is formed when segments intersect portions of a circle and create arcs.These segments in effect 'intercept' parts of the circle. The picture below shows examples of intercepted arcs.
The measure of an arc = the measure of its central angle.
Therefore the measure of =85
The measure of =360° −85°=275°