y+1/4=x+2/3 2x-y=1----------------------y=2x-1 代入2x-1+1/4=x+2/32x-x=2/3+1-1/4x=17/12y=2x-1=2*17/12-1=11/6 x/2+y/3=1/2 x/2=y/3 代入x/2+x/2=1/2x=1/2y=3*x/2=3*1/4=3/4