You are given the points (3,-7) and (0,-2).
Let's find the slope.
m = [-7 - (-2)]/(3 - 0) = -5/3
Use the point-slope form. Either points you plug in will give you the same slope-intercept form.
y - (-2) = (-5/3)[x - 0]
y + 2 = (-5/3)x + 0
y = (-5/3)x - 2
y - (-7) = (-5/3)[x - 3]
y + 7 = (-5/3)x + (15/3)
y + 7 = (-5/3)x + 5
y = (-5/3)x - 2