For the first problem, the answer is choice A) 8
The notation "a32", with the "32" as a subscript, means "the address of row 3, column 2". The value that is in row 3, column 2 is the value 8. The row number is always listed first when it comes to addressing in matrices.
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For the second problem, we can only add together matrix A and matrix D, as they are the same size (2x2 matrices). We cannot add any other pairs together because of the size mismatch. In order to add any two matrices, they must have the same number of rows and the same number of columns.
Another example would be adding two 3x1 matrices together. They both have 3 rows and 1 column.