If you put this into y=mx +b form this become y= 2/3 x +b
Since the point (-2,-6) is on the graph you can substitute these value for x and y to solve for b
-6 = (2/3) (-2) +b
-6 = -4/3 +b
b= -6 +4/3
b - 4 2/3 or - 14/3
So final equation is y = (2/3)x -(14/3)