We have to find the slope of line RS.
We can see line RS goes through points R = (-4, 3) and S = (-1, 2) so the slope will be:
slope = 3 - 2 / -4 - (-1)
slope = 1 / -4 + 1
slope = - 1 / 3
Now any line that is parallen to line RS must have the same slope of line RS then:
slope = - 1 / 3
Answer: the slope of any line parallel to line RS equals - 1 / 3.