Answer:
120 = m PR
Explanation:
The angle formed outside =1/2(difference of intercepted arcs)
60 = 1/2 (major arc - minor arc)
60 = 1/2 (longPR - short PR)
120 = long PR - short PR
long PR = 360 - short PR since a circle is 360 degree
120 = 360 - short PR - short PR
120 = 360 -2 short PR
Subtract 360 from each side
120-360 = -2 short PR
-240 = -2 short PR
Divide by -2
120 = m PR