If you are trying to find the slope using only these two points then you should first take note of what your X and Y values are. For instance, 12 & 11 are your X values and -18 & 12 are your Y values. Knowing this you can now find your slope by doing y2-y1/
x2-x1. You will get the fraction -30/1 or -30 which is your slope. Hope that made sense!
