In order to find the slope m of the line, you use the following formula:
where (x1,y1) and (x2,y2) are the coordinates of two points on the line.
In the given graph you have the following two points:
(-3 , 1)
(2 , -2)
you use the previous coordinates to replace in the formula for the slope m, just as follow:
Hence, the slope of the given line is m = -3/5