Subtraction, by definition, is simply the addition of the opposite of the number. (ie. a-b=a+(-1)(b)=a+(-b))

The same is applicable to matrices. See matric multiplication by a scalar for the multiplication of a matrix by a number.

```   / 3   10   2 \       / 2   8   1 \
A=|  2   9    4  |   B=|  10  6   8  |
|  13  4    2  |     |  4   14  10 |
\ 3   6    7 /       \ 6   7   4 /
```

As in the addition of matrices, in order to subtract matrices, the dimensions of both matrices must be the same. Matrix A is a 4x3 matrix and Matrix B is a 4x3 matrix, thus they can be subtracted from each other.

To compute the differce A-B, you will add the opposite of B to A, or A-B=A+(-1)(B).

```
/ 2   8   1 \     / -2   -8   -1 \
-1B=-B= -1|  10  6   8  | = |  -10  -6   -8  |
|  4   14  10 |   |  -4   -14  -10 |
\ 6   7   4 /     \ -6   -7   -4 /
/ 3   10  2 \     / -2   -8   -1 \     / 1   2   1 \
A+-B=|  2   9   4  | + |  -10  -6   -8  | = |  -8  3   -4 |
|  13  4   2  |   |  -4   -14  -10 |   |  9   10  -8 |
\ 3   6   7 /     \ -6   -7   -4 /     \ -3  -1  3 /
```

Note that in the subtraction of matrices, just as in subtraction of anything else, the order does matter. A-B is NOT the same a B-A.