In the figure below, F,G,H and J are collinear. FG, GK, and HK are lone segments of equivalent length, and the measure of JHK is 120 degrees. What is the degree measure of GFK?

The answer would be 30 degrees because points F, G, H, and J are collinear, all you would have to do is figure out /_GHK by subtracting 180 degrees from it.
Like this :
JHK = 180 degrees - 120 degrees = 60 degrees