in y=mx+b, m represents the slope. Let's try to get your equation to look like that. We can see that on the left side, the y is not yet alone so we must try to accomplish that. to do that we divide by -8 from the -8y, but we must also do that to the other side. you would get y=-2/8x-5/8. then we would simplify the -2/8x into -1/4x. Now it is y=-1/4x-5/8 and that resembles y=mx+b. m is slope and -1/4 is m.
