3)
[tex]~~~~~~~~~~~~\textit{middle point of 2 points } \\\\ (\stackrel{x_1}{-2}~,~\stackrel{y_1}{9})\qquad (\stackrel{x_2}{-7}~,~\stackrel{y_2}{7}) \qquad \left(\cfrac{ x_2 + x_1}{2}~~~ ,~~~ \cfrac{ y_2 + y_1}{2} \right) \\\\\\ \left(\cfrac{ -7 -2}{2}~~~ ,~~~ \cfrac{ 7 + 9}{2} \right)\implies \left( \cfrac{-9}{2}~~,~~\cfrac{16}{2} \right)\implies \left( -4\frac{1}{2}~~,~~8 \right)[/tex]