Im having trouble with Gauss-Jordan elimination of augmented matrices.

I can do it for square matrices but what do I do if, for example, a 4 * 5 matrix crops up.

Eg: 1 1 -1 0 1 | 3

1 2 -4 1 -2| 4

2 3 -5 2 -6| 8

3 4 -6 2 -5| 11

eventually eliminates to:

1 1 -1 0 1 | 3

0 1 -3 1 -3| 1

0 0 -2 2 -9| -1

0 0 0 -9 37| -1

but I need to have just one non-zero column on the last row in order to begin back substitution???

Any help is much appreciated! I have a test in 5 hours!!!