The equation of the line is:
y = -x + 9
To identify slope, we use rise/run. However, the line goes down, so there is automatically a negative slope. From the point (0,9), the graph goes to (1,8) which is down one point and to the right one point (-1/1). Because x itself is a variable and equals 1 by default, our slope is -x. The y-intercept is the b in y = mx+b. It is the point on the y-axis where the graph begins. In this case, the y-value of the starting point is (0,9).
The equation of the line is y = -x + 9.