解方程：x+y+z=6 15x+7y+9z 请问x=?,y=?z=?

(x+y-z)(x-y+z)= 解方程一;{x+y-z=6,x-3y+2z=1,3x+2y-z=-7.②{3x+4z=7,2x+3y+z=9,5x-9y 解方程组{x(x+y+z)=6,y(x+y+z)=12,z(x+y+z)=18 X+Y+Z=? 解方程：{2x+3y+z=7,x+y+z=4,3x+y-z=-4 解方程{3x -y+z=4 2x+3y-z=12 x+y+z=6 2x 6y z=7和3x 9y z=8求x y z=几解二愿以此方程,我知道x y 解方程组 x+y+z=-7 x-y=12 x+y-z=6 2x+4y+3z=9 3x-2y+5z=11 5x-6y+7z=13 这个方程怎么解? x*z/(20+x+y)=3; z/(20+x+y/2)=0.45; x*z /(x+20)=9; 请问此方程如何解 f(x,y,z,w)=x*(x+y)*(x+y+z)*(x+y+z+w) 解方程:x+2y+3z=8 x+3y+5z=6