5. Basically you need to add the terms in the same positions in both matrices, so:
2 + 6 = 8 1 + (-4) = -3
-3 + 2 = -1 0 + 4 = 4
So the answer would be the first one :)
6. This one is not possible as to add or subtract matrices they must have the same order, which is not the case with this pair.