Answer: to find velocity, simply put (d2-d1) over (t2-t1) or d/t.
Explanation: To find velocity, divide the change in distance by the change in time. On a graph, pick two points and find the slope of one portion of the line.
Why the slope?
Well this is like your normal x vs. y graph. X being the time and y being your distance.
To find the slope for this, it uses the same formula: (Y2-y1) / (x2-x1)
Hope this helps!!!
BTW, this is physics.