Can you please explain how to answer this?
What is a solution for the following system?
x-4y+z=2 and -x+4y-2z=8
a) x=4s+12, y=s, z=-10
b) x=s+4, y=3s, z=-4
c) x=2s+5, y=s, z=-12
d) x=s, y=4s, z=-12
add the two equations
>>>z=-10
that allows only a) to be the answer.