3x+y+2z=28,5x-3y+z=7,试求x+y+z的值!

已知x+4y+3z=3x-2y-5z=0,求x+2y-z/2x-3y+7z的值 x/3=y/4=z/5,求x+y+z/3x-2y+z的值, 若x/3=y/4=z/5,求x+y+z/3x-2y+z的值. x+2y+3z=20,x+3y+5z=31,求x+y+z的值 已知x/4=y/5=z/6 求x+y+z/3x-2y+z的值 已知x/4=y/5=z/6,求x+y+z/3x-2y+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. 已知x+y-z=0,2x-y+2z=0 求（3x-2y+5z)/(5x-3y+2z)的值 已知x,y,z满足3x+7y+z=5 4x+10y+z=3 求x+y+z的值 已知x、y、z满足{3x+7y+z=5 ,求x+y+z的值 {4x+10y+z=3 已知有理数x,y,z满足|x-z-2|+|3x-6y-7|+(3y+3z-40)^2=0,求x,y,z的值 已知x,y,z,同时满足方程x+3y-5z=0,2x-y-3z=0求x：y：z的值