If $A = \begin{bmatrix}1 & -3\\-3 & 5\end{bmatrix}$ and $AB = \begin{bmatrix}-11 & -3 & 7\\13 & 1 & 9\end{bmatrix}$ determine the first and second columns of B.

I'm not quite sure how to do this. My intuition would be to "divide" (sorry, I don't know what the correct term is, I'm just using MATLAB terminology here) AB by A, but that would result in a 3x2 matrix, not a 2x3 matrix...

The program is recommending using an augmented matrix for $A=b\_1$ and $A=b\_2$, where $b\_x$ is a column from B, but I'm not sure how that helps me.