And if we want to solve for m, we want to cancel out the b. So let me rewrite this top equation just the way it's written over here. So we have m times the mean of the x squareds plus b times the mean of... Actually, we could even do it better than that. One step better than that is to actually, based on the work we did in the last video, we can just subtract this bottom equation from this top equation. So let me subtract it, or let's add the negative. So if I make this negative, this is negative, this is negative, what do we get? We get m times the mean of the x's minus the mean of the x squareds over the mean of x, over the mean of the x's.