Answer: A) 12
Step-by-step explanation: As ∠EGF,∠ADF and ∠BCF are equal let it be equal to β
So, tanβ=[tex]\frac{perpendicular}{base}[/tex]
tanβ=[tex]\frac{EF}{EG}[/tex] for triangle FEG
and tanβ=[tex]\frac{BF}{BC}[/tex] for triangle FBC
and by using above two equations,we get
[tex]\frac{EF}{EG}[/tex]=[tex]\frac{BF}{BC}[/tex]
i.e. 6/4=18/BC
hence, BC=12
