Pre-Requisite
The matrix must have the same dimensions (so same # of rows and same # of columns)
How?
If the dimensions are the same you subtract 1 element from the other in the order it was given
Eg: A = 1 2 3 4 5 6 B = -1 3 -2 -3 4 1 A - B = 2 -1 5 7 1 5
In this example the elements are being subtracted with their cooresponding element