Answer:
6
Step-by-step explanation:
You can memorize these for the smaller shapes
for equilateral polygons:
triangle: 60
square: 90
pentagon: 108
hexagon: 120
Otherwise, I believe the formula is the total degrees in a polygon (s-2)*180 where s is the number of sides.
So the measure of each angle on average would be (s-2)*180/s.
There (s-2)*180/s = 120
180(s-2) = 120s
180s-360 = 120s
60s = 360
s = 6
