The Solution.
The sum of interior angles of a polygon is given by:
[tex]\begin{gathered} \text{Sum = (n-2)180} \\ \text{where n =number of sides} \end{gathered}[/tex]
Substituting 6 for n in the formula above, we get
[tex]\begin{gathered} \text{Sum =(6-2)180} \\ \text{Sum = 4}\times180=720^o \end{gathered}[/tex]
So,
[tex]\begin{gathered} 78+134+136+132+2x+x=720 \\ \text{collecting like terms, we get} \end{gathered}[/tex][tex]\begin{gathered} 480+3x=720 \\ 3x=720-480 \\ 3x=240 \\ \text{Dividing both sides by 3, we get} \\ x=\frac{240}{3}=80^o \end{gathered}[/tex]
Thus, the correct answer is 80 degrees (option C)
