The midpoing of the segment is (4, 0), so the value of m is 0.
How to find m?
if point P divides the line segment AB, then P is the midpoint of said segment.
Remember that for two points (x₁, y₁) and (x₂, y₂) the midpoint is given by:
M = ( (x₂ + x₁)/2, (y₂ + y₁)/2)
Here we have the points (2, 3) and (6, -3), the midpoint will be:
( (2 + 6)/2, (3 - 3)/2)
(4, 0)
So the value of m must be zero.