Out of the choices given, the gemstones had approximately 20 edges. This correct answer is D, 20. The answer can be figured out by using " Euler's Polyhedral Formula." The correct formula for this particular question is shown here; F = 12, V = 10
V - E + F = 2
10 - E + 12 = 2
-E + 22 = 2
-E = -20
E = 20. I hope that helps you.
