خطا
$\begin{align} & \alpha +\beta +\theta ={{180}^{\circ }}\Rightarrow \alpha ={{180}^{\circ }}-(\beta +\theta ) \\ & \tan \alpha =\tan ({{180}^{\circ }}-(\beta +\theta ))\Rightarrow \tan \alpha =-\tan (\beta +\theta ) \\ & -\frac{4}{3}=-\frac{\tan \beta +\tan \theta }{1-\tan \beta \tan \theta } \\ \end{align}$ از طرف دیگر با توجه به شکل $\tan \alpha =\frac{x}{4}$ و $\tan \beta =\frac{2}{3}$ است. $\Rightarrow -\frac{4}{3}=-\frac{\frac{2}{3}+\frac{x}{4}}{1-(\frac{2}{3})(\frac{x}{4})}\Rightarrow \frac{4}{3}=\frac{8+3x}{12-2x}\Rightarrow x=\frac{24}{17}$