8. Let real numbers $x, y$ satisfy the conditions $\left\{\begin{array}{l}x-y+1 \geqslant 0, \\ y+1 \geqslant 0, \\ x+y+1 \leqslant 0,\end{array}\right.$ then the maximum value of $2 x-y$ is
The coordinates of the three vertices of the feasible region are $A(-2,-1), B(-1,0), C(0,-1)$, so the maximum value of $2 x-y$ is 1.