If you look at the circle, the numbers given add up to 11. The interior angles of a circle always add up to 180 degrees. If you add zeroes onto the numbers given they become 30, 20, and 60. These add up to 110. Out of the choices given the only one that would make sense is 7, because if you add a zero onto 7 it becomes 70. 110 + 70 = 180.
Therefore, the answer is 7.
Hope this helps!
~Ash