The equation of the line is:

This equation is equal to "9" in part (a) and "-3" in part (b).
How do we solve the equation in part(a) and part(b) using graph?
We look at y = 9 and see at which x value it intersects with the graph.
Similarly, we look at y = -3 and see at which x value it intersects with the graph.
a)
We draw a horizontal line at y = 9. The point where it intersects the line drawn, we draw a vertical line to connect to the x-axis. So, it connects at x = -4. This is the solution. Let's check it algebraically as well.

b)
We draw a horizontal line at y = -3. The point where it intersects the line drawn, we draw a vertical line to connect to the x-axis. So, it connect at x = 4. Tis is the solution. Let's check algebraically:
