Question

Which expression gives the z-coordinate of the solution of the system x+2y-2z=3?

Answer 1

From the system of equation
x+2y-2z=3
3x-y+z=16
x+z=7
we solve the system as follows:
add equation i and ii
x+2y-2z=3
6x-2y+2z=32

7x=35
x=5
thus
z=2

2y+5-4=3
2y=2
y=1

hence
x=5, y=1 z=2