Well, to find the equation, understand y=mx+b (slope-intercept equation format). M= slope and B= y-intercept. The line is going down, so the slope will be negative. Do the rise over run (or divide the rise by the run) to find the slope. Plug in your slope for M. The y-intercept is where the line intercepts the y-axis. Plug it in for B. Then you have your equation.