[tex]\bf \textit{middle point of 2 points }\\ \quad \\
\begin{array}{lllll}
&x_1&y_1&x_2&y_2\\
% (a,b)
&({{ 6}}\quad ,&{{ -1}})\quad
% (c,d)
&({{ -3}}\quad ,&{{ -13}})
\end{array}\qquad
% coordinates of midpoint
\left(\cfrac{{{ x_2}} + {{ x_1}}}{2}\quad ,\quad \cfrac{{{ y_2}} + {{ y_1}}}{2} \right)
\\\\\\
\left(\cfrac{-3+6}{2}~,~\cfrac{-13-1}{2} \right)[/tex]
and fairly sure you know how much that is.
