The midpoint between two complex numbers x+yi and u+vi is given by:
[tex]\frac{x+u}{2}+\frac{y+v}{2}i[/tex]Plugging the values of the numbers given we have:
[tex]\frac{3+7}{2}+\frac{-12+6}{2}i=\frac{10}{2}-\frac{6}{2}i=5-3i[/tex]Therefore the value of b is -3
