3a-b+c=4①
2a+b-c=6②
2a+3b-c=12③
①+②
5a=10
a=2
①+③得
5a+2b=16
10+2b=16
b=3
a=2 b=3带入①得
c=1有2题1/2*x-y=1/3*x y=x5/6① x-y-1=z② 4x-5y+3z=5③①带入②得x-5/6x-1=zz=x/6-1④①④带入③4x-5*(5x/6)+3(x/6-1)=54x-25x/6+x/2-3=51/3x=8x=24y=20z=3