//To have the lines parallel, the gradients must be the same.
y -- 6 = 1/2 (x - 9)
y + 6 = 1/2 x -9/2
y = 1/2 x - 10.5
36/42
multiply the top and bottom by 6.
7 x 6 = 42
6 x 6= 36
15.2
16 + 12 + 8 + 22 + 25 + 8 = 91 / 6 = 15.16 = 15.2
It's a hexagon.
The formula of the sum of internal angles in the polygon:

Therefore
