These are easy, we just have to average the corresponding coordinates.
First we do a few one dimension ones, the midpoint of points on a number line:
1. 9 & 6
[tex]\dfrac{9 + 6}{2} = \dfrac{15}{2}[/tex]
2. -2 & 7
[tex]\dfrac{-2 + 7}{2} = \dfrac{5}{2}[/tex]
3. -3 & -13
[tex]\dfrac{-3 + -13}{2} = -8[/tex]
For the rest of these we're in 2D, the Cartesian plane.
4. (0,0), (9,3)
[tex]\left( \dfrac{0+9}{2}, \dfrac{0+3}{2} \right) = ( \frac 9 2, \frac 3 2)[/tex]
5. (-2,1), (3,6)
[tex]\left( \dfrac{-2+3}{2}, \dfrac{1+6}{2} \right) = ( \frac 1 2, \frac 7 2)[/tex]
6. (-3, 14), (10, -4)
[tex]\left( \dfrac{-3+10}{2}, \dfrac{14+-4}{2} \right) = ( \frac 7 2, 5)[/tex]
