check the picture below.
thus
[tex]\bf \textit{middle point of 2 points }\\ \quad \\
\begin{array}{lllll}
&x_1&y_1&x_2&y_2\\
% (a,b)
&({{ 4}}\quad ,&{{ 6}})\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}} + {{ 4}}}{2}\quad ,\quad \cfrac{{{ y}} + {{ 6}}}{2} \right)=(\underline{7,2})\implies
\begin{cases}
\cfrac{x+4}{2}=\underline{7}\\\\
x+4=14\\
x=14-4\\
\boxed{x=10}\\
----------\\
\cfrac{y+6}{2}=\underline{2}\\\\
y+6=4\\
y=4-6\\
\boxed{y=-2}
\end{cases}[/tex]
