Make the extension lines of ED and AB intersect with g point.

Triangle OFD is similar to triangle AFE,

AF/DF=EF/F0=AE/DO

Triangle ODG is similar to triangle AEG,

AE/DO=AG/OG

Connect BC, triangle ABC is similar to triangle age.

AC/AB=AE/AG

Triangle ODG is similar to triangle AEG.

AE/AG=OD/OG=2/5

OB=OA=OD

So AG/OG=(AO+OG)/OG=7/5.

So AF/DF=AE/DO=AG/OG=7/5.