||Two thousand years ago all Chinese with an education could use a bunch of red and black sticks as an handy pocket calculator. They could of course do addition, subtraction, multiplication and division with very large numbers. More surprisingly, they had efficient algorithms for square and cubic roots and for solving systems of linear equations. For the latter they used matrix algebra – converting the coefficient matrix to a diagonal one. I will show how it was done, including an example of an equation system with four unknowns from Jiuzhang Suanshu, Nine Chapters on the Mathematical Art. It was written about year 100 and was the standard textbook on math in China for a very long time to come.