Step-by-step explanation:
8-3 = 5,
3-5 = -2 = the x coordinate of B
-2-4 =-6,
-2-6 =-8 = the y coordinate of B
(-2,-8) is the point B
A is 5 to the right of the midpoint, so B is 5 to the left of the midpoint
A is 6 up from the midpoint so B is 6 down from the midpoint
