The first point, 0.2 0.2, is the starting point. So it would not count. It would be 0
The second point, 0.2 -0.5, is how many units down?
The third point, 0.6 -0.3, is how many units away from the second point?
The fourth and final point, 0.6 -0.8, is how many units away from the third?
Add all of these individual distances together, and you should get the answer!