Notice that all the sides of the triangle have the same measure. Then, it is an equilateral triangle. On such a triangle, all the internal angles have a measure of 60°. Then:
[tex]4x+8=60[/tex]
Substract 8 from both sides:
[tex]\begin{gathered} 4x+8-8=60-8 \\ \Rightarrow4x=52 \end{gathered}[/tex]
Divide both sides by 4:
[tex]\begin{gathered} \Rightarrow\frac{4x}{4}=\frac{52}{4} \\ \Rightarrow x=13 \end{gathered}[/tex]
Therefore:
[tex]x=13[/tex]
