1/4X+1/2（12-X)=X
x+2(12-x)=4x
x+24-2x=4x
24=5x
x=24/51/4X+1/2(12+12-X)=X你少了个121/4X+1/2（12-X)=Xx+2(24-x)=4xx+48-2x=4x48=5xx=48/5