DISPLACEMENT-TIME graphs question

[Rasofia]

1. It's a displacement time graph with coordinates (0,0), (3,-3),(5,-3), (9,5) The lines are all linear.
The question first asks 'Calculate the velocity for each section 0-3s, 3-5s,5-9s. I know how to do that part (it's -1m/s, 0m/s, and 2m/s).
But the other part of the question asks: What distance has been traveled in 9s?
How can I find the distance traveled in the total 9 seconds with a displacement/time graph??
(By the way, displacement is the y-axis, time is the x-axis)

 

[spl-083902]

I'm sure you know this equation
$$v=\frac{d}{t}$$
and just do it in sections