# euclidean geometry – How to get the angle in a trapezoid formed by two triangles?

The problem is as follows:

Find the value of angle $$angle BCA$$ or $$x$$.

The alternatives given in my book are as follows:

$$begin{array}{ll} 1.&30^circ\ 2.&20^circ\ 3.&10^circ\ 4.&40^circ\ end{array}$$

The thing here is without any further hints. I’m stuck.

I was only able to spot.

$$triangle ABC$$ is isosceles,

$$triangle DBC$$ is isosceles

But I can’t find any other relationship. What else to do?. How to solve this relying only in euclidean geometry postulates?. Can someone help me here?.

Should congruence be used here or what?.