已知x/2=y/3=z/5,则x+y-2z/x-y=( ) 怎样想和做?

已知(x+2y)/3=(y+3z)/4=(z+5x)/5,则x:y:z= 已知x+2y/3=y+3z/4=z+5x/5,则x:y:z=? 已知x+2y/3=y+3z/4=z+5x/5,则x:y:z= 已知方程组4x-5y+2z=0 x+2y=3z 则x:y:z 已知{x+z=5 y+z= - 2 y+x=3 ,则x+y+z等于过程。。 已知2x+5y+4z=15.7x+y+3z=14 则x+y+z=? 已知x+4y-3z=0,4x-5y+2z=0,则x：y：z 已知x+4y=3z,4x-5y=-2z,则x:y:z 已知x-y/x+y=y+z/2(y-z)=z+x/3(z-x),求证8x+9y+5z=0THX.. 已知(x+y)(x+z)=x,(y+z)(y+x)=2y,(z+x)(z+y)=3z,求x,y,z 已知：4x-5y+2z=0 x+4y-3z=0则：(x*x+y*y+z*z)/(x*y+y*z+z*x)=____. 已知关于x y z的方程组2x-3y+5z=7 x+2y-3z=8,则4x+y-z= 已知x,y,z,满足2/x=3/(y-z)=5/(z+x),则(5x-y)/(y+2z)的值为多少? 已知x-y+z=0,3x+y-5z=0,则x+y+z/x+2y-3z=? 已知x-y+z=0.3x+y-5z=0,则x+y+z/x+2y-3z=_______ 已知xyz不等于0,且{x+3y+5z=0 x2+3y+z=0,则x.x+y.y-2z.2z/3x.3x+2y.2y+z.z=? 已知x/y+z=y/x+z=z/x+y,分式(x+2y+3z)/(2x+5y-2c)有意义时的值 已知x,y,z满足2/x=3/y-z=5/z+x,则5x-y/y+2x的值快快