设大皮球x个,小皮球y个: x+y=80 x/(x+y)=0.6-->3x+3y=5x-->6x+6y=10x y/(x+y)=0.4-->2x+2y=5y-->6x+6y=15y==>10x-15y=0 x+y=80-->10x+10y=800 10x-15y=0==>25y=800,y=32,x=48设再买进一...