The angles 2x and 36 are vertical angles, which means that they are angles opposite to the same vertex and thus they are equal:

Now we have to solve this equation to find the value of x.
To solve for x, divide both sides of the equation by 2:

On the left-hand side, the 2 on the numerator and the 2 on the denominator cancel each other and we are left only with x:

And on the right-hand side 36/2 is equal to 18:

Answer: x=18