For slope intercept form, you need to identify the slope and y-int of the graph.
y=mx+b, where m=the slope and b=the y-int
The y-int is (0,5), because it's at this point where the line crosses the y-axis. To find the slope, look at rise over run. Immediately you know that the slope is going to be negative because the line slopes down. The slope is -2/1, or just -2, because from one point to the other, the line goes down two points and to the right one point.
So, if m=-2 and b=5, you can set up the equation as y= -2x+5
