Answer:
B
Step-by-step explanation:
GI is made up of the segments GH and HI. In other words:

We know that GH is 2 and GI is 7. Substitute:

Subtract 2 from both sides:

So, our answer is B.
And we're done!
for an angle of 780°, we can say that is really a 360° + 360° + 60°, so two full revolutions plus an extra 60°. Check the picture below, with the coterminal in green.