An arc is a part or a portion of a circle.
An intercepted arc is created when segments(chords,secants,etc..) intersect a part of the circle. These segments in effect 'intercept' parts of the circle. The picture below shows examples of intercepted arcs.
You can think of the intercepted arc as the crust in a piece pizza.
The measure of an arc = the measure of its central angle.
Therefore the measure of =85
The measure of =360° −85°=275°