Chapter 4.2, Problem 35E

Each of the matrices in Problems $35\text{-}42$ is the result of performing a single row operation on the matrix $A$ shown below. Identify the row operation.

$A=\left.\left[\left.\begin{array}{cc}-1& 2\\ 6& -3\end{array}\right|\right.\begin{array}{c}-3\\ 12\end{array}\right]$

$\left.\left[\left.\begin{array}{cc}-1& 2\\ 2& -1\end{array}\right|\right.\begin{array}{c}-3\\ 4\end{array}\right]$