For a polygon with N sides, the sum of the interior angles must be equal to:
[tex]A=(N-2)\times180[/tex]
Because the presented polygon has 6 sides, we calculate the total of the sum as:
[tex]A=(6-2)\times180=4\times180=720[/tex]
Now, let's use the given values to find x:
[tex]\begin{gathered} 720=78+134+136+132+2x+x=480+3x \\ 3x=720-480=240 \\ x=\frac{240}{3}=80\degree \end{gathered}[/tex]
From the present solution, the correct answer is D) 80°
