[tex]\bf \textit{middle point of 2 points }\\ \quad \\
\begin{array}{lllll}
&x_1&y_1&x_2&y_2\\
% (a,b)
&({{ -17}}\quad ,&{{ 7}})\quad
% (c,d)
&({{ x}}\quad ,&{{ y}})
\end{array}\qquad
% coordinates of midpoint
\left(\cfrac{{{ x_2}} + {{ x_1}}}{2}\quad ,\quad \cfrac{{{ y_2}} + {{ y_1}}}{2} \right)[/tex]
[tex]\bf \left( \cfrac{x-17}{2}~,~\cfrac{y+7}{2} \right)=\stackrel{\textit{midpoint}}{(-23,10)}\implies
\begin{cases}
\cfrac{x-17}{2}=-23\\\\
x-17=-46\\
\boxed{x=-29}\\
----------\\
\cfrac{y+7}{2}=10\\\\
y+7=20\\
\boxed{y=13}
\end{cases}[/tex]
