Solve the system of equations: $$\begin{aligned} & x _ { 1 } + 2 x _ { 2 } - 3 x _ { 3 } = 5 \\ & 2 x _ { 1 } - x _ { 2 } + 4 x _ { 3 } = 7 \\ & 3 x _ { 1 } + 4 x _ { 2 } + x _ { 3 } = - 2 \end{aligned}$$