若x+y=3 y+z=4 z+x=5 则y的值是

若3x+7y+z=5,4x+10y+z=3,则x+y+z=? 若x/2=y/3=z/4,则3x-2y+5z/x+y+z= 若x+y:y+z:z+x=3:4:5,则x:y:z=?(急,) 若x+y+z=3y=2z,则x/x+y+z=? 若x,y,z成等差数列,则(z-x)^2-4(x-y)(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)=____. (x+y):(y+z):(z+x)=3:4:5 3x+y-z=-4已知(x+y):(y+z):(z+x)=3:4:5 ；3x+y-z=-4求x y z 三元一次方程组题目x+y-z=11 y+z-x=5 x-y+z=1x+y=4 y+z=3 x+z=5若已知x-3y+2z=0 2x+3y-8z=0, 且xyz≠0,则x:y:z= 若{x-3y+z=0,3x+3y-4z=0,则x:y:z=? 若x/3=y/2=z/5,则2x-3y-z/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x+2y/3=y+3z/4=z+5x/5,则x:y:z= 若2x=3y=5z,则3x-2y+z/x+y-z 若4x=7y+5z,2x+y=z,则x:y:z的值为 已知x+y=3,当y+z=4,x+z=5,则x+y+z等于() 已知2x+5y+4z=15.7x+y+3z=14 则x+y+z=? 如果3/x=4/y=5/z,则（x+y+z）/（x-y-z）=