Answer
$(6.2,-6.65)$
Work Step by Step
The midpoint of the two points $(x_1,y_1)$ and $(x_2,y_2)$ is the point $\left(\dfrac{x_1+x_2}{2},\dfrac{y_1+y_2}{2}\right)$
$\left(\dfrac{4.6+7.8}{2},\dfrac{-3.5-9.8}{2}\right) = \left(6.2,-6.65\right)$