The first thing to do is find where the line intercepts the y-axis, which is at positive 9 so you'll add a +9 to the end of your equation. Next you find the slope and since it's going down left to right, you know it is a negative. Now slope is found by change in y divided by change in x. And since both change and y and change in x are both 1, 1/1 is 1. And since you know it's negative that means the slope is -x. Altogether you get y= -x+9
