Question 760669
from 3:  
z=3x

1 plus 2: 
(2x-y+z)+(x+y+z)=3+6

3x+2z=9

3x+2(3x)=9

9x=9

x=1

so z=3

from 1: 
x+y+z=1+y+3=6

y+4=6

y=2


Solution: (1,2,3)



:)