$\begin{array}{l} \sin \left( {3x + \dfrac{\pi }{3}} \right) = \dfrac{{ - \sqrt 3 }}{2}\\ \Leftrightarrow \left[ \begin{array}{l} 3x + \dfrac{\pi }{3} = - \dfrac{\pi }{3} + k2\pi \\ 3x + \dfrac{\pi }{3} = \pi + \dfrac{\pi }{3} + k2\pi \end{array} \right.\\ \Leftrightarrow \left[ \begin{array}{l} x = \dfrac{{ - 2\pi }}{9} + k\dfrac{{2\pi }}{3}\\ x = \dfrac{\pi }{3} + \dfrac{{k2\pi }}{3} \end{array} \right.\left( {k \in Z} \right)\\ + x \in \left( {0;\dfrac{\pi }{2}} \right) \Rightarrow x = \dfrac{\pi }{3},x = \dfrac{{4\pi }}{9} \Rightarrow 2 \end{array}$