This application of Editorial Editex S.A. solve systems of linear equations of 3 unknowns by the methods of Cramer and Gauss. It includes the following sections:  - Theory: contains a document in PDF format with a summary of contents.  - Practice: allows the resolution of systems through the methods of Cramer and Gauss, as well as a geometric interpretation of them.  - Test: allows you to perform a self-assessment with 10 test-type exercises collected randomly.  - Problems: this section is inten