The problem is as follows:

> 
> In a triangle $\triangle{ACB}$, $AC=20\,m$ it is also known $\angle{A}=2\angle{B}$ and the length of the foot of the height drawn from vertex $C$ to point $B$ is equal to $30\,m$ Find angle $C$.
> 
> 
> 

The choices given in my book are as follows:

$\begin{array}{cc}
1.&30^{\circ}\\
2.&60^{\circ}\\
3.&90^{\circ}\\
4.&53^{\circ}\\
5.&75^{\circ}\\
\end{array}$

According to the official answers sheet the answer here is choice 3.

I am not sure how to make the right drawing or the interpretation here. Can someone help me with some sketch?

From then on, what is this?. Congruency, any special case of the triangle theorems or what?. This problem belongs to the section about basic relations in triangles thus I believe that it can be solved with those without requiring additional things.

What sort of construction using only euclidean geometry can be done here to solve the problem?

Please help me here, I don't know what to do