In the diagram, GB = 2x + 3..
 Triangle F D E has centroid G. Lines are drawn from each point to the midpoint of the opposite side to form line segments F A, D C, E B. The length of line segment F G is 5 x and the length of line segment G A is x + 9.
 What is GB?
 5 units
 10 units
 15 units
 30 units