You left out the Answer part. In the Solution part you perform the calculations (e.g. Gauss) to calculate the inverse of $A$. But ever so often, the last tiny help for the reader, namely a summarising answer sentence "The inverse of matrix $A$ is ..." is missing. Without that, one wonders if the student gave up calculations in the middle, did not know what to do next or did not see the answer-forest because of the many calculation-trees. –  Hagen von Eitzen Sep 2 '12 at 9:13