the equation of slope is rise/ run, or the change in x over the change in y. The actual formula is (x2 - x1)/ (y2-y1). On your graph, you should look at the line, and find 2 points that you know the coordinates of. With the 2 coordinates, the first number is always x and the 2nd number is always y (x,y). Choose one of your coordinate pairs, and take the x value and subtract it from the other x value of the other coordinate pair. Then, in the same order, take the y value from your first coordinate pair and subtract it from the y value in the other coordinate pair. Lastly, divide the x difference by the y difference and that's your slope!
Example:
two coordinate pairs: (-2,-1) and (4,3)
-2 and 4 are your x values, and -1 and 3 are your y values.
4-(-2) = 6, and 3-(-1) = 4
therefore, your slope is 6/4, or you can reduce that fraction to 3/2
your finalized slope is 3/2
hope that made sense!