Use back-substitution to solve the system $$\begin{alignedat}{3} 2x + 2y \amp {}+{} \amp z \amp {}={} \amp 10\\ y \amp {}-{} \amp 4z \amp {}={} \amp 9\\ \amp\amp 3z \amp {}={} \amp -6 \end{alignedat}$$ Give the solution as an ordered triple.