Determine the measure in degrees of the angle indicated with an arc.

the degree with an arc is marked (3x)$^\circ$, and we know that a striaght line consists of 180 degrees in total, so 180-82.5=3x+2x=97.5

5x = 97.5

x = 19.5

3x = 19.5 $\cdot$ 3 = $\boxed{58.5^\circ}$