I don't know how to find the value of x for geometry isoceles and equilateral triangles.

Given data:
The given isosceles triangle.
In an isoscels triangle 2 angles are always equal, the expression for sum of all the angles in atriangle is,
[tex]\begin{gathered} 120^{\circ}+x+x=180^{\circ} \\ 2x=60^{\circ} \\ x=30^{\circ} \end{gathered}[/tex]Thus, the value of x is 30 degrees.