I can not find any useful online tool that solves you a system of equations using Gaussian elimination and LU decomposition. So just a system like: -3X+4X+9X+4x=-2 9X+2X+1X-5X=2 etc. Just about 4 lines. several lines. So basically an online tool where you can just plug in the -3,4,9,4,-2 etc and it solves it for you. Same with the LU decomposition for systems like this one. And, does somebody know of a website where Gaussian elimination and LU explained in detail ? I know how to do Gaussian elimination, but I'm used to do it in a different way. Solve the equations for whatever, but I'm talking about just taking the numbers, put them in a matrix and then solve it. I'm not quite sure how that works. LU decomposition is tricky too, imo. Just can't find anything that's useful. I would appreciate any help!