å设 Sâ³ABC = X
è¿A & DåBCåå足M & Nï¼â³ABCä¹é«AMä¸â³DBFä¹é«DNçæ¯ä¾ = AB : BD = 7 : 5ï¼â³ABCä¹åºBCä¸â³DBFä¹åºBFçæ¯ä¾ = 8 : 3ï¼å æ¤Sâ³ABC : Sâ³DBF = 7x8 : 5x3 = 56 : 15
=> Sâ³DBF = 15X/56
åçå¾ Sâ³ADE = 6X/35 & Sâ³CEF = X/4
=> â³DEF = â³ABC - â³DBF - â³ADE - â³CEF = X - 15X/56 - 6X/35 - X/4 = 43.5
X * ( 1 - 75/280 - 48/280 - 70/280) = 87X/280 = 43.5 => X = 140
Sâ³ABC = 140