DrawDG∥BF
AD is mention and E is mid-point of AD
⇒AE=ED
By converse of mid-point theorem
F is mid-point of AGandAF=FG−−(1)
Similarly, In BCFD is midpoint of BC&DC∥BF
G is midpoint of CAandFG=GC−−(2)
by(1)and(2)AF=FG=GC−−−(3)
From figure, AF+FG+GC=AC
3AF=AC
AF=13×AC
AF=13×6
AF=2cm