수학이에요 중2이에요

be : ef = bc : df = 4 : 1.

be = bf * 4/5.

bg : gf = bc : af = 4 : 5.

bg = bf * 4/9.

ge = bf * (4/5 - 4/9)

= bf * 16/45.

bg : ge = 4/9 : 16/45

= 20 : 16 = 5 : 4.

ab = 20.