To find conjecture about regular polygon, use the formula

Where, n = number of sides of the regular polygone
1) Triangle
n =3
So, Conjecture of the triangle =

= 120
2) Square
n =4
So, Conjecture of the square =

= 90
3) Pentagone
n = 5
So, Conjecture of the pentagon =

= 72
4) Hexagone
n = 6
So, Conjecture of the pentagon =

= 60.
Answer:
0
Step-by-step explanation:
Given that,
6m - 2n=0
=>6m=2n
=>n=3m [divide both side by 2]
& mn=12
Now,
216c - 8n³
= 216m³- 8(3m)³
=216m³- 8 .27m³
=216m³- 216m³
=0