Answer
$(6.2,-6.65)$
Work Step by Step
We know that the midpoint of the line segment whose endpoints are $(x_{1},y_{1})$ and $(x_{2},y_{2})$ is the point with coordinates $(\frac{x_{1}+x_{2}}{2},\frac{y_{1}+y_{2}}{2})$.
Therefore, a line with endpoints $(4.6, -3.5)$ and $(7.8,-9.8)$ will have a midpoint of $(\frac{4.6+7.8}{2},\frac{-3.5+(-9.8)}{2})=(\frac{12.4}{2},\frac{-13.3}{2})=(6.2,-6.65)$.
