Linear Albegra Calculators:
Linear Algebra: Vector, Matrix, Determinant, Simultaneous https://keisan.casio.com/menu/system/000000001250
http://www.math.odu.edu/~bogacki/cgi-bin/lat.cgi
Khan Academy has a a dozen videos about Linear Algebra, Vectors and Spaces: https://www.khanacademy.org/math/linear-algebra/vectors-and-spaces/null-column-space/v/introduction-to-the-null-space-of-a-matrix
Here are Patrick Just Math videos on Linear Algebra (58 of them!-usually they are shorter than Khan's) https://www.youtube.com/user/patrickJMT/search?query=Linear+Algegra
Solving for a 3x3 Matrix http://patrickjmt.com/finding-the-determinant-of-a-3-x-3-matrix
WikiBOOKS: https://en.wikibooks.org/wiki/Linear_Algebra