Question

2x-y+3z=9 ,x+y+z=6,x-y+z=2

Answer 1

(1)
(2)
(3)
(2)-(3), 2y=4
              y=2
after that just substitute into (1) and (2)
then you can find the x and Y by minus the after substitute equation

Answer 2

From the first 2 equations, we will get
3x+4z = 15
From the last 2 equations, we will get
x+z = 4

by solving these two, 
we will get the values of x as 1 and z as 3
substitute it in any equation, we will get y as 2