Find the explicit formula for the general solution to the linear iterative systems with the following coefficient matrices:
(a) $\left(\begin{array}{rr}-1 & 2 \\ 1 & -1\end{array}\right)$,
(b) $\left(\begin{array}{ll}-2 & 7 \\ -1 & 3\end{array}\right)$
(c) $\left(\begin{array}{rrr}-3 & 2 & -2 \\ -6 & 4 & -3 \\ 12 & -6 & -5\end{array}\right)$,
(d) $\left(\begin{array}{rrr}-\frac{5}{6} & \frac{1}{3} & -\frac{1}{6} \\ 0 & -\frac{1}{2} & \frac{1}{3} \\ 1 & -1 & \frac{2}{3}\end{array}\right)$.