Hello!
From looking at the graph, I believe that the length of the line segment must be C, 30 units. The length of the line must be 30 because on the graph, you can see that the line from 0 to 20 would have a length of 20. Now if you look at the line from -10 to 0, the length of that line would be 10. Now add the lengths of the lines 20 and 10 together. Once you've done that the measure of the line segment will be 30.
I hope this helps!
