Hi Sherry,
The basic form of an equation of a line in the slope intercept form is y = mx + b
However, given two points, we have to begin with the point slope form which is y-y1 = m(x-x1)
From the points given we can calculate the slope, m
m = y2-y1
------
x2-x1
m = (-20-5)/(-9-6) = -25/-15 = 5/3
and
y-5 = (5/3)(x-6) <--- point slope form
y-5 = (5/3)x - 10
y = (5/3)x - 5 <---- slope intercept form