这道题怎么做？---**Extraction Content:** **Question Stem:** 如图所示，已知 $BD=4$, $CD=2$, $\angle ADB = 60^\circ$, $\angle C = 45^\circ$, 求 $\angle B$ **Translation of Question Stem:** As shown in the figure, it is known that $BD=4$, $CD=2$, $\angle ADB = 60^\circ$, $\angle C = 45^\circ$, find $\angle B$. **Chart/Diagram Description:** * **Type:** Geometric figure (Triangle). * **Main Elements:** * **Vertices:** Points labeled A, B, C. * **Point:** Point D on the line segment BC. * **Segments:** Lines connecting A to B, A to C, A to D, and the line segment BC. D is located between B and C. * **Labels and Annotations:** * Point A is at the top vertex. * Points B, D, C are on a horizontal line segment, from left to right in that order. * The length of segment BD is labeled as 4 (in blue text below BD). * The length of segment CD is labeled as 2 (in blue text below CD). * Angle $\angle ADB$ is labeled as $60^\circ$ (next to point D). * Angle $\angle C$ (which is $\angle ACB$) is labeled as $45^\circ$ (near point C).