Explanation:
the change rate or slope is the ratio (y coordinate change / x coordinate change) when going from one point on the line to another.
formally, in an interval [a, b] the change rate is therefore
(f(b) - f(a))/(b - a)
in the graph we look for points with integer coordinates.
like (3, 5) or (2, 2) or (0, -4).
so, let's use any pair of them, e.g. (3, 5) and (2, 2).
the direction from what point to what point does not matter, as long as we use the same for x and y.
say, we go from (2, 2) to (3, 5) :
x changes by +1 (from 2 to 3).
y changes by +3 (from 2 to 5).
so, the slope or change rate is
+3 / +1 = 3
FYI - if we go from (3, 5) to (2, 2)
x changes by -1 (from 3 to 2).
y changes by -3 (from 5 to 2).
so, the slope is
-3 / -1 = 3
so, you see the direction does not matter. the slope is the same.