The formula for midpoint is:
[tex](\frac{x_{1} +x_{2} }{2 } , \frac{y_{1} +y_{2} }{2} )[/tex]
Since the points are (5, 12) and (-4, 8) the equation would be...
[tex](\frac{5 +(-4)} 2, \frac{12+8 }{2} )[/tex]
[tex](\frac{1}{2} , \frac{20}{2}[/tex]
(.5, 10)
Hope this helped!