Answer
See solution
Work Step by Step
Row reducing, we get $\begin{bmatrix}
11&7&-7&-9&-6\\
0&65&-10&-5&191\\
0&0&0&1&-2\\
0&0&0&0&1
\end{bmatrix}$. From here, we can see that we can either remove column 2 or 3 and get a 4 by 4 matrix that has a pivot in each row. There cannot be a pivot in each row if there are only 3 columns, so we can't delete more than 1 column.
