Question 250951
Add 1 and 3,
{{{x+y+z+2x+y-z=9+3 }}}
4.{{{3x+2y=12}}}
Multiply 3 by 3 and add to 2,
{{{6x+3y-3z+x-2y+3z=9+8}}}
5.{{{7x+y=17}}}
Multiply 5 by -2 and add to 4.
{{{-14x-2y+3x+2y=-34+12}}}
{{{-11x=-22}}}
{{{x=2}}}
Now work backwards,
{{{7x+y=17}}}
{{{14+y=17}}}
{{{y=3}}}
.
.
{{{x+y+z=9}}}
{{{2+3+z=9}}}
{{{z=4}}}
.
.
.
(x,y,z)=(2,3,4)