Answer:
98
Step-by-step explanation:
for a 4 sided polygon you can only draw one diagonal from one vertex so it forms 2 triangles.
For 5 sides you get 3 triangles
For 6 sides - 4
For 7 sides - 5
For 8 sides - 6
Looks like we get 2 less triangles than the number of sides in the polygon
Answer for 100 sides is 98 triangles.
