Point g is the centroid of triangle abc. use the given information to find the value of x?
18. cg = 3x + 7 and ce = 6x
19. fg= x+8 and af = 9x-6
20. bg= 5x-1 and dg = 4x-5
find it in each situation

Because g is the centroid of the triangle abc, then ag = bg= cg 
here cg = 3x+7 and bg= 6x
3x+7 = 6x
7=6x-3x
7=3x
x=7/3


for the question to be "workable", af is probably the median, with f on bc 

remember the centroid cuts the median in the ratio of 2: 1, or ag: gf = 2: 1
  then fg: af= 1: 3 
(x+8)/(9x-6) = 1/3
  9x - 6 = 3x + 24
  6x = 30
  x = 5