x/3 - (y+1)/6 =3 2x—y+1=18 (设为①式)2(y- x/2)=3(y- x/18) 2y—x=3y—x/6 —5x/6=y (设为②式) 把②式代入①式得 2x+5x/6+1=18 解得x=6代入②式 解得y=—5