I hope you meant 720 not 780...If that's so, then yes. And to find 2 negative coterminal angles, we subtract 360 and 720.
If the given angle is in standard position, find two positive coterminal angles and two negative coterminal angles.
Angle = 120 degrees
How would you solve this? Do you add 360 and 780 to it so it becomes two positive coterminal angles?
Yeah, you've got the right idea. Just add 360 to 120 and add 720 to 120 to get the two positive coterminal angles of 480 and 840.
Then, to get the negative coterminal angles, subtract 360 from 120 and subtract 720 from 120. I'll leave this to you.
Note, I noticed in your original message your wrote 780 instead of 720. I didn't know if this was a typo or not. Just make sure you use 720 because 360 * 2 = 720.
Hope this helps.