Answer:
[tex]=\left(-\frac{19}{2},\:-2\right)[/tex]
Step-by-step explanation:
[tex]\left(\frac{x_2+x_1}{2},\:\:\frac{y_2+y_1}{2}\right)\\\\\left(x_1,\:y_1\right)=\left(-10,\:5\right),\:\\\left(x_2,\:y_2\right)=\left(-9,\:-9\right)\\\\=\left(\frac{-9-10}{2},\:\frac{-9+5}{2}\right)\\\\Simplify \\=\left(-\frac{19}{2},\:-2\right)[/tex]