Here is the question I am having difficulty with:

If the echelon form of the coefficient matrix of a homogeneous system of linear equations is:

1 2 3 0 2 1

0 0 1 1 2 0

0 0 0 1 2 1

0 0 0 0 0 0

0 0 0 0 0 0

Find a set of basic solutions of this system

Any tips on where to start?