设大姑娘x人,中年妇女y人,老太婆z人
x+y+z=100
6x+3y+1/6z=100
则3x+3y+3z=300
6x+3y+1/6z-3x-3y-3z+200=0
17/6z-3x=200
z=(1200+18x)/17
因为6x