are lin.indep, if from
Than, let see the system:
Solve it...
If you get than vectors is lineary indipendent, else not.
Your are not completely done in transforming your matrix to row-reduced echelon form.
As GnomeSain mentioned in the above post, you should place the given cloumn vectors into a 4x3 matrix, and its row reduced echelon form looks like this:
Now, can you tell, what is the rank of the matrix?
Again look at GnomeSain's post, to know how you would be able to determine linear independence by knowing the rank of the row reduced matrix!