You can put this solution on YOUR website! You didn't post the question. We're not mind readers.
I'm thinking you need to come up with an equation in slope intercept form for a line that has a slope m=-1 and a y intercept of b=-4 (that's my best guess on what you need?????)
y=mx+b plug in your values
y=-1x-4
y=-x-4 this is would be the equation