2x-3y+z=28 3x+4y+z=56 4x+5y-z=66

x=y/z=z/3,x+y+z ＝12,求2x+3y+4z是多少, x/2=y/3=z/5 x+3y-z/x-3y+z 试证明(x+y-2z)+(y+z-2x)+(z+x-2y)=3(x+y-2z)(y+z-2x)(z+x-2y) (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuai 2x+5y+4z=6,3x+y-7z=-4,x+y-z=? 已知x:y:z=3:4:5,3x+2y-4z=18.求：x+y+z. {2x+3y-4z=-5 x+y+z=6 x-y+3z=10 已知2x+5y+4z=6 3x+y-7z=-4求x+y-z 2x+5y+4z=0,3x+y-7z=0,则x+y-z=? 解方程组：x+y+z=4,x+y+2z=5,3x+y-z=6 已知2x+5y+4z=15.7x+y+3z=14 则x+y+z=? x/3=y/4=z/5,求x+y+z/3x-2y+z的值,