Using a slope intercept equation (y=mx+b), we can find the equation of this line. First, find two perfect points on the graph.
(-1,3) and (0,1)
Use rise/run
The distance between the two points is down 2, right 1. So the slope (m), is -2/1 (negative because the line is a negative line, going right.)
Last, the y-intercept is b. Simply find where the line crosses the y-axes. Which is at 1.
Now put all the numbers in:
y=-2/1x+1
Hope this helped!