Answer: B = (6,-8)
Explanation:
first the midpoint formula is

then you take the x co-ordinate of A and substitute it into one of the x values in the first part of the formula:

then solve it like an equation:

then you take the y co-ordinate of A and substitute it into one of the y values in the second part of the midpoint formula:

then solve it like an equation:

∴ the answer is x=6, y= -8
which is expressed as a point, B(6,-8)