Subtraction is very similar to addition except it subtracts the numbers.
For multiplication, Matrix 1 columns must be equivalent to Matrix 2 rows. The resulting matrix will be Matrix1 rows by Matrix2 columns. For the inverse, transpose, trace, and determinant operations you only need to fill in Matrix 1 text area and Matrix 1 row and column fields. That means you cannont perform the inverse operation with that given matrix. That matrix may not be singular.