@tomleslie Thx a lot for your quick reponse. The solution is a pefect but I need or I would like to know step by step how maple comes to the solution like the example "tutor app gaussian elemination". First do that, then second step do this...and so on. Thx a lot for your help.

@Kitonum Thank you so much Sir. 

@tomleslie  ouuuu ok Tomleslie a lot of thank youssssss. Stay safe.

Thank you for your quicks response.