xz/(20+x+y)=3; z/(20+x+y/2)=0.45; xz /(x+20)=9; 请问此方程如何解

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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

令20+x=a,则x=a-20,
∴(a-20)z/(a+y)=3 ①,z/(a+y/2)=0.45 ②,(a-20)z/a=9 ③,
③/①得(a+y)/a=3,即y=2a,
将y=2a代入②,得z=0.9a,
将z=0.9a代入③,得0.9(a-20)=9,∴a=30
故x=10,y=60,z=27.

x*z/(20+x+y)=3; z/(20+x+y/2)=0.45; x*z /(x+20)=9; 请问此方程如何解解不定方程x+y+z=20 3x+2y+z=50 2x+6y+z=7与3x+9y+z=8此方程的解 (x+y-z)(x-y+z)= 试证明(x+y-2z)+(y+z-2x)+(z+x-2y)=3(x+y-2z)(y+z-2x)(z+x-2y) (20%x+30%y+45%z)/(x+y+z)=35%这个方程怎么解? 3x-y+z=3 2x+y-3z=11 x+y+z=12 解方程解方程：{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 2分之x=3分之y=5分之z x+y+z=20 求x,y,z x+2y+3z=20,x+3y+5z=31,求x+y+z的值解方程一;{x+y-z=6,x-3y+2z=1,3x+2y-z=-7.②{3x+4z=7,2x+3y+z=9,5x-9y