Can someone please explain to me the Guass-Jordan method to solve a system of equations?

My homework question is:

Use the Gauss-Jordan method to solve the system of equations.

4x-6y=54

20x-30y=270

I am sure that if someone would simplify the method for me (I guess explain it to me a little more clearly) I would be able to figure it out. I don't want the answer, I would like to figure it out on my own, but just need someone to lead me in the right direction.