To calculate the slope you have to use the following formula.
Where
(x₁, y₁) are the coordinates of one point of the line
(x₂, y₂) are the coordinates of another point of the line
The slope of a line is always the same, regardless the segment you use to calculate it.
For line segment AC
The point are:
A (3, 2)
C (0, 1)
The slope is
For line segment AD
The point are
A (3, 2)
D (9, 4)
The slope is
For both line segments the slope is m=1/3