Which of the following is an example of a system of three linear equations in theee variables A) y+z=12
3y+z=18
2y-4z=21

B) x+y+7z=8
2x+z-3w=2
x-4y+w=1

C) x+2x=15
2x=12
2x+x-3x=20

D) x+y+z=5
2x-3y+z=7
x+2y-4z=2

1) no, because a solution must be an ordered triple pair (x,y,z)

2) { x+y+z=5    

   { 2x-3y+z=7      

   { x+2y-4z=2

3) infinity many solutions

4) use equations (1) and (2) to eliminate y

5) solve one equation for one of its variables  

Step-by-step explanation:

should be 100% on the quick check if you put those answers

i got 10.28 but that rounds up to 10.3