we know that
The centroid of a triangle is the intersection of the three medians of the triangle. The coordinates of the centroid are also two-thirds of the way from each vertex along that segment
so
in this problem
The point G is the centroid of the triangle ABC
 ------> equation A
 ------> equation A
we have

substitute in the equation A and solve for x
 
 
 
 
 
 
 ------> equation B
 ------> equation B
we have

substitute in the equation B and solve for GF
 
 
 
 
substitute the value of x
 
 
therefore
the answer is
She used 
 , but the correct statement is
, but the correct statement is 
