设ΔABC的面积为S,
∵AD=1/3AB,AF=4/5AC;SΔBDE=2/3×1/4S=1/6S,
∴SΔADF=1/3×4/5×S=4/15S;SΔCE=3/4×1/5S=3/20S
∴S阴影=(1-4/15-1/6-3/20)S=25/60SΔABC,
∴S=25×60/25=60
设ΔABC的面积为S,
∵AD=1/3AB,AF=4/5AC;SΔBDE=2/3×1/4S=1/6S,
∴SΔADF=1/3×4/5×S=4/15S;SΔCE=3/4×1/5S=3/20S
∴S阴影=(1-4/15-1/6-3/20)S=25/60SΔABC,
∴S=25×60/25=60