math(Please help Urgent!!)
posted by Abbey on .
In triangle ABC, D is the centroid and M is the midpoint of segment AC. If BD=x+9 and DM=6, find MB. Answer choices: 9 , 3, or 18.

This is almost identical to the question you posed in
http://www.jiskha.com/display.cgi?id=1225892455
follow the method I described there. 
its B