Question 1192036
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In this current state, there isn't enough information to answer parts (b) and (c)


I'll only address part (a)


Draw any hexagon you wish. It doesn't need to be concave.
From one of the six vertex points, draw segments to connect to the other non-adjacent vertices. 
You should draw 3 such additional segments.


This splits the hexagon into 4 triangles.
The sum of the angles of any triangle is 180 degrees. 


Therefore, the angles of any hexagon always add to 180(4) = 720 degrees.
This applies to concave hexagons as well as convex hexagons.


You could use the formula
S = 180(n-2)
where n = 6 and you'll get the same result. In fact, what I've discussed earlier is a visual proof of why that formula works.
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