Part I:
Slope is (change in y)/(change in x), often represented using the letter m.
m = (4 -1)/(2 -1) = 3/1 = 3
The slope of AB is 3.
Part II:
The point-slope form of the equation of a line with slope m through point (h, k) is usually written
y -k = m(x -h)
Adding k, you can rearrange this to
y = m(x -h) +k
For m = 3 and (h, k) = (4, 2) we can fill in the numbers as
y = 3(x -4) +2
Eliminating parentheses puts this in slope-intercept form.
y = 3x -10 . . . equation for line p