Question 56375
x-y+2z=7 --> Equation1
2x+z=4 --> Equation2
x+5y+z=9 --> Equation3


Since Equation2 only have x and z variable, we'll eliminate y from the other 2 equation 


Equation1 --> x-y+2z=7 (times 5) --> 5x - 5y + 10z = 35
Equation3 --> x+5y+z=9 ------------>  x + 5y +   z =  9 (add both equations)


will have 6x + 11z = 44 --> Equation 4



Equation 4 --> 6x + 11z = 44------------> 6x + 11z = 44
Equation 2 --> 2x +  z =  4 (times 3)---> 6x +  3z = 12 (subtract equations)
8z = 32
z = 4


Substitute z on Equation2 --> 2x + 4 =4 --> x=0

Substitute z and x to Equation1 --> 0-y+2(4)=7 --> y=1

Therefore x=0 , y=1, z=4