(5x+y-z)/6=(3x+2z)/4=(3y+z)/5=2(5x+y-z)=12 ①(3x+2z)=8 ② (3y+z)=10 z=10-3y ③联立求解把③带入①得 5x+y-10+3y=125x+4y=22 ④把③带入②得3x+20-6y=8 3x-6y=-12 x-2y=-4 ⑤2⑤+④得7x=14x=2y=3z=1