若点$P$的坐标为$(\frac{x-1}{3}$，$2x-9)$，其中$x$满足不等式组$\left\{\begin{array}{c}5x-10⩾2(x+1)\\ \frac{1}{2}x-1⩽7-\frac{3}{2}x\end{array}\right.$，求点$P$所在的象限．