Ah, well the question only asked for the solutions in between zero and two pi.
All the general solutions are given, the only thing you have to do is determining the solutions in $\displaystyle 0<x<2\pi$.
For example one of the solutions was:
$\displaystyle x=\frac{-\pi}{6}+2k\pi$
And so the ony solution for $\displaystyle x\in ]0,2\pi[$ is:
$\displaystyle x=\frac{11\pi}{6}$