If $ A = \begin{bmatrix} 1 & 2 & 3 \\ 1 & 3 & -1 \\ -1 & 1 & -7 \end{bmatrix}$ find `A^{-1}`. Hence solve the following equations. `x+y-z=3`, `2x+3y+z=10`, `3x-y-7z=1`