Lineare Gleichungssysteme mit 3 Unbekannten (8. Klasse)

Löse die folgenden Gleichungssysteme mit einem Verfahren deiner Wahl:

1. $$\begin{array}[t]{rcrcrcrcr}4\,x & \hspace{-0.7em} + & \hspace{-0.7em} 3\,y & \hspace{-0.7em}- & \hspace{-0.7em} \,\,z & \hspace{-0.7em} = & \hspace{-0.7em} -38\\ \,x & \hspace{-0.7em} - & \hspace{-0.7em} 6\,y & \hspace{-0.7em} - & \hspace{-0.7em} 2\,z & \hspace{-0.7em} = & \hspace{-0.7em} 19\\ -5\,x & \hspace{-0.7em} + & \hspace{-0.7em} \,\,y & \hspace{-0.7em} + & \hspace{-0.7em} \,\,z & \hspace{-0.7em} = & \hspace{-0.7em} 23\end{array}$$
2. $$\begin{array}[t]{rcrcrcrcr}2\,x & \hspace{-0.7em} + & \hspace{-0.7em} \,\,y & \hspace{-0.7em} + & \hspace{-0.7em} 7\,z & \hspace{-0.7em} = & \hspace{-0.7em} 50\\ \,x & \hspace{-0.7em} + & \hspace{-0.7em} \,\,y & \hspace{-0.7em} - & \hspace{-0.7em} 4\,z & \hspace{-0.7em} = & \hspace{-0.7em} -10\\ -2\,x & \hspace{-0.7em} + & \hspace{-0.7em} 5\,y & \hspace{-0.7em} - & \hspace{-0.7em} 2\,z & \hspace{-0.7em} = & \hspace{-0.7em} 5\end{array}$$
3. $$\begin{array}[t]{rcrcrcrcr}3\,x & \hspace{-0.7em}- & \hspace{-0.7em} \,\,y& \hspace{-0.7em} & \hspace{-0.7em} & \hspace{-0.7em} = & \hspace{-0.7em} 4\\ 2\,x & \hspace{-0.7em} + & \hspace{-0.7em} 2\,y & \hspace{-0.7em} + & \hspace{-0.7em} 4\,z & \hspace{-0.7em} = & \hspace{-0.7em} -40\\ 5\,x & \hspace{-0.7em} - & \hspace{-0.7em} 3\,y& \hspace{-0.7em} & \hspace{-0.7em} & \hspace{-0.7em} = & \hspace{-0.7em} 16\end{array}$$
4. $$\begin{array}[t]{rcrcrcrcr}3\,x & \hspace{-0.7em} + & \hspace{-0.7em} 3\,y& \hspace{-0.7em} & \hspace{-0.7em} & \hspace{-0.7em} = & \hspace{-0.7em} -9\\ \,x & \hspace{-0.7em} - & \hspace{-0.7em} 7\,y & \hspace{-0.7em}- & \hspace{-0.7em} \,\,z & \hspace{-0.7em} = & \hspace{-0.7em} -9\\ -3\,x & \hspace{-0.7em} - & \hspace{-0.7em} 2\,y & \hspace{-0.7em} - & \hspace{-0.7em} 2\,z & \hspace{-0.7em} = & \hspace{-0.7em} -3\end{array}$$