let's recall that, arc's angle measures come from the central angle they're in.
if this intercepted arc is 80°, and is intercepted by an angle stemming from the center, namely a central angle, then the angle is also 80°. Check the picture below.
Step-by-step explanation: it’s been half an hour and they ran the 12 miles so in an hour which is double half an hour they ran two times what they did in half an hour