Answer
$$(-0.5,-5.5)$$
Work Step by Step
The coordinates $(x_{m},y_{m})$ of the midpoint of the segment joining the points $(x_{1},y_{1})$ and $(x_{2},y_{2})$ are given by
$$x_{m}=\frac{x_{1}+x_{2}}{2}$$ and $$y_{m}=\frac{y_{1}+y_{2}}{2}.$$
Substitute $x_{1}=-1$, $y_{1}=-8$, $x_{2}=0$ and $y_{2}=-3:$
$$x_{m}=\frac{-1+0}{2}=-0.5$$ and $$y_{m}=\frac{-8+(-3)}{2}=-5.5.$$