https://people.revoledu.com/kardi/tutorial/LinearAlgebra/RREF.html
Linear Algebra tutorial: Reduced Row Echelon Form (RREF)
Linear algebra tutorial with online interactive programs
linear algebraechelon formtutorialreducedrow
https://origami24.net/apps/matrix/gauss.html
Gaussian elimination, Row echelon form Calculator
Calculate the Row echelon form of a Matrix (up to 9 x 9) with Gaussian elimination
gaussian eliminationechelon formrowcalculator