I've been following Khan Academy to try and teach myself how to invert matrices, howevever I tried to invert a 3×3 matrix and I am not sure where I have gone wrong.
Picture of my answer:
I tried to invert $A$ but my answer is wrong. I would appreciate any help given.
Link of KhanAcademy tutorial I was following: https://www.khanacademy.org/math/algebra-home/alg-matrices/alg-determinants-and-inverses-of-large-matrices/v/inverting-3x3-part-1-calculating-matrix-of-minors-and-cofactor-matrix