Answer
B is the inverse of A
Work Step by Step
When there is an inverse of a matrix $A A^{-1} = I$ (the Identity Matrix)
$AB = \begin{bmatrix} 2 & -7 & 11 \\-1 & 11 & -7 \\ 0 &3 & -2 \end{bmatrix} \begin{bmatrix} 1 & 1 & 2 \\2 & 4 & -3 \\ 3 & 6 & -5 \end{bmatrix} =\begin{bmatrix} 1 & 0 &0\\ 0 & 1 &0 \\0 &0&1\end{bmatrix}$
and $BA = \begin{bmatrix} 1 & 1 & 2 \\2 & 4 & -3 \\ 3 & 6 & -5 \end{bmatrix} \begin{bmatrix} 2 & -7 & 11 \\-1 & 11 & -7 \\ 0 &3 & -2 \end{bmatrix}=\begin{bmatrix} 1 & 0 &0\\ 0 & 1 &0 \\0 &0&1\end{bmatrix}$
Since $AB=BA$ equals the identity matrix, B is the inverse of A.
