Given $A$ and $b$ in Exercises 11 and $12,$ write the augmented matrix for the linear system that corresponds to the matrix equation $A \mathbf{x}=\mathbf{b} .$ Then solve the system and write the solution as a vector.
$$
A=\left[\begin{array}{rrr}{1} & {2} & {4} \\ {0} & {1} & {5} \\ {-2} & {-4} & {-3}\end{array}\right], \mathbf{b}=\left[\begin{array}{r}{-2} \\ {2} \\ {9}\end{array}\right]
$$