已知3x+7y+z=315和4x+10y+z=420,求x+y+z

已知3x+7y+z=315和4x+10y+z=420,求x+y+z 知3x+7y+z=315,4x+10y+z=420,求x+y+z=? 已知3X+7Y+Z=6 4X+10Y+z=7 求X+Y+Z=? 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2x+5y+4z=6 3x+y-7z=-4求x+y-z 已知5x=3y,4z=7y,求x:y:z 已知x+4y+3z=3x-2y-5z=0,求x+2y-z/2x-3y+7z的值 已知有理数x、y、z满足条件|x-z-2|+(3x-6y-7)^2+|3y+3z-4|=0,求x、y、z 已知方程组2x-3y-4z=0和x+y+z=0,并且z≠0,求x：y与y：z 已知3X=4X,5Y=6Z求X+Y：Y+Z 已知x,y,z满足{4x-3y-3z=0,x-3y+z=0.（x不等于0,y不等于0,z不等于0）求x/z和y/z的值