急急急!数学难题!若2x+3y+z=5,2x+y+3z=3. 则z+y+z的值?

急急急!数学难题!若2x+3y+z=5,2x+y+3z=3. 则z+y+z的值? 已知x、y、z满足2x+3y+z=48 x-2y+2z=56 3x+5y+3z=52 则x+y+z的值为多少 急 若x/3=y/4=z/5,求x+y+z/3x-2y+z的值. 若2分之x+y=3分之y+z=5分之x+z 且x+y+z=18 求x,y,z的值 已知x:：y：z=3：4：5,(1)求x+y分之z的值；（2）若x+y+z=6,求x,y,z. 若x,y,z,满足3x+2y+z=5,2x+y-3z=1.y是非负数.求z的取值范围 已知x/3=y/5=z/4,求x+y+z/y和x+y-z/y-x的值,2种方法.急等. 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) 若4x=7y+5z,2x+y=z,则x:y:z的值为 若x:y:z=2:3:4,求x+y+z/x-2y+3z的值 x/3=y/4=z/5,求x+y+z/3x-2y+z的值,