From the diagram we get that the given triangle is an isosceles triangle, then, its interior angles are 30°, x°, and x°.
Now, recall that the interior angles of a triangle add up to 180 degrees, then we can set the following equation:
[tex]30\degree+x\degree+x\degree=180\degree\text{.}[/tex]
Solving the above equation for x we get:
[tex]\begin{gathered} 30+2x=180, \\ 30+2x-30=180-30, \\ 2x=150, \\ \frac{2x}{2}=\frac{150}{2}, \\ x=75. \end{gathered}[/tex]
Answer: First option.
