y₂₋y₁ / x₂-x₁ if you have two points you can plug them in and find the slope using this.
If it is on a graph you can look at two points and count the rise over run, for example if one point is (0, 0) and another is (2, 3) then from the first point it goes up 2 and over 3, so the slope would be 2/3
