Answer:
8.3 mm
Step-by-step explanation:
An enneagon is a polygon with 9 sides, also called nonagon.
In a regular polygon, all sides are congruent, so the length of any side is the perimeter divided by the number of sides.
length of a side = perimeter/number of sides
length of a side = 74.7 mm/9 = 8.3 mm
