What is matrix subtraction?
You subtract the corresponding elements to get your result.
This is one of the easier matrix operations. Here is an example:
[a b c]-[g h i] = [a-g, b-h, c-i]
[d e f]. [j k l] ... [d-j,. e-k,. f-l]
Ignore the "."; it's the only way to space things right now.
Since we are subtracting corresponding elements, the matrices must have the same dimensions; the answer must also have the same dimension.