It's simple to add and subtract matrices, but they must always be the same size for it to work. The answers are always the same size too. Check it out:
All you do is add the entries in each corresponding place:
Subtraction? Same idea.
Now we just subtract the entries in each place:
Looks tough, but as long as you don't lose your place, you're golden. But remember, they must be the same size. And a 2 × 3 is not the same as a 3 × 2, for example.