Solve x,y,z

Question

X+y+z=4

X+y+2z=5

4x+4y+6z=18

 

Solve for x,y,z

Answer 1

1) X+y+z=4
2) X+y+2z=5
3) 4x+4y+6z=18

 

if you multiply #1 by -1 it changes to 

-x-y-z=-4

 

if you add #2 by your new #1

x+y+2z-x-y-z=5-4

 

simplified you get 

z=1

 

plugging that into all the problems you get

1)x+y+1=4 or x+y=3

2)x+y+2(1)=5 or x+y=3

3)4x+4y+6(1)=18 or 4x+4y=12 or 4(x+y)=12 or x+y=3

 

at this point x and y are interchangeable so 

x=1 and y=2  or x=2 and y=1