Question

x+y+z=10
2x+y+z=12
x-y+2z=9
resolver el sistema

Answer 1

${-} \left \{ {{x+y+z =10} \atop {2x+y+z=12}} \right. . \left \{ {{-x-y-z =-10} \atop {2x+y+z=12}} \right. . \left \{ {{-x =-10} \atop {2x=12}} \right. . \left \{ {{x=2} .$

Answer 2

X+y+z=10 ...(1)

2x+y+z=12 ...(2)

x-y+2z=9 ...(3)

Restando (2) con (1)

2x+y+z-(x+y+z)=12-10

x=2

Sumando (2) y (3)

3x+3z=21

x+z=7

pero x=2

2+z=7

z=5

reemplazando x=2 ,z=5 en (1)

2+y+5=10

y=3

respuesta x=2,y=3,z=5