systems of first degree equation, mathematics. which solutions of the
system?
observation: this system is determined.
  https://i.stack.imgur.com/QeLWz.png
By substituting $ x = -4y$ in the rest of the two equations you will get the below as the answer.The solution is $$x=0,y=0,z=0$$
By substituting $ x = -4y$ in the rest of the two equations you will get the below as the answer.The solution is $$x=0,y=0,z=0$$