Ok, so:
To find the slope of the segment, we have to take two points:
Let's take: A(2,6) and B(1,3).
We calculate the slope as this:
m =( ( y2 - y1 ) / ( x2 - x1 )).
Where A( x1, y1) and B( x2, y2) are the points we took.
Then, m = (3 - 6) / (1-2), this is m = -3/-1, and that's equal to m=3