We have the following:
Since the sides are equal, it means that all the angles are equal, we also know that the sum of the 3 angles within a triangle is always 180°, therefore
[tex]\begin{gathered} 5x+5x+5x=180 \\ \text{solving for x:} \\ 15x=180 \\ x=\frac{180}{15} \\ x=12 \end{gathered}[/tex]
The value of x is 12
