2x+y-z=8
x+z=-5
2y-3z=21

z=-5; x=0 ; y=3

Step-by-step explanation:

2x= -2z -10; -2z-10+y-z=8; y-3z-10=8; y-3z=18

2y-3z=21; 2y=3z+21; y= 1.5z+10.5; y-3z=18

1.5z+10.5-3z=18; -1.5z+10.5=18; -1.5z=7.5; z=-5

x+z=-5; x-5=-5; x=0; 2y-3z=21; 2y+15=21; 2y=6; y=3

2x+y-z=8; 2(0)+3-(-5)=8; 3+5=8; 8=8

answer: c

because if you look at the chart you can see a pattern and compare it to the question he simplify out your

but i think the formula is f(x)=6x

i believe the correct answer is b.