Finding all matrices that commute with a given matrix

[esmeco]

I have this question as homework from my Algebra class:
A square matrix X is called exchangeable with A if AX=XA.Determine the set of permutable matrices with

My question is,how do I find that set?I know that a matrix to be permutable all rows and columns must be the same and that a square matrix is composed by the same number of rows and columns.
Thanks in advance for the help!

 

[matt grime]

You defined exchangable, not permutable, so who knows?

 

[esmeco]

By exchangeable i meant permutable...

 

[matt grime]

You defined what it means for X to be exchachangable *with A*, not what it means for X to be exchangable, or permutable.