Explanation:
your teacher gave you even the formula. so, what is still not clear ?
in regular words, the slope of a line is the ratio
y coordinate difference / x coordinate difference
when going from one point on the line to another.
so, we have here (-2, 1) and (3, 2).
x changes by +5 (from -2 to 3).
y changes by +1 (from 1 to 2).
so, the slope is +1/+5 = 1/5