(* Linear Algebra: Theory and Applications *)
(* Ward Cheney & David Kincaid *)
(* JBPub.com (c) 2008 *)
(* File: exp128.mat *)
(* Example 1.2.8      *)

A = {{1,2,3,20},{4,5,6,47},{7,8,9,74},{10,11,12,101}
RowReduced[A]