The sum of the external angles of a polygon is equal to 180 degrees.
Therefore,
[tex](2x+9)+(x+12)+(2x+7)+(2x+11)+(2x+15)=180[/tex]
Solving the above equation for x,
[tex]\begin{gathered} (2x+x+2x+2x+2x)+(9+12+7+11+15)=180 \\ 9x+54=180 \\ 9x=180-54 \\ 9x=126 \\ x=\frac{126}{9} \\ x=14 \end{gathered}[/tex]
Therefore, the value of x is 14.
