[tex]\bf ~~~~~~~~~~~~\textit{middle point of 2 points } \\\\ (\stackrel{x_1}{4}~,~\stackrel{y_1}{10})\qquad (\stackrel{x_2}{x}~,~\stackrel{y_2}{y}) \qquad \left(\cfrac{ x_2 + x_1}{2}~~~ ,~~~ \cfrac{ y_2 + y_1}{2} \right) \\\\\\ \left( \cfrac{x+4}{2}~~,~~\cfrac{y+10}{2} \right)~~ = ~~\stackrel{midpoint}{(2~~,~~5)}\implies \begin{cases} \cfrac{x+4}{2}=2\\[1em] x+4=4\\ \boxed{x=0}\\[-0.5em] \hrulefill\\ \cfrac{y+10}{2}=10\\[1em] y+10=20\\ \boxed{y=10} \end{cases}[/tex]
