MathNet 2019-part-02 — 184 problems (EN–VI) Question 97

Let $\triangle ABC$ be a triangle such that $\angle CAB = 20^\circ$, and let $D$ be the midpoint of the side $\overline{AB}$. If $\angle CDB = 40^\circ$, find $\angle ABC$. (Tamara Srnec)