Subtracting a negative number is like adding the positive one.
Example: 10 - (-2) is like 10 + 2 = 12.
In general assume you have A - (-B) = X and you want to find X.
You can add (-B) to both sides: A - (-B) + (-B) = X + (-B) hence A = X - B and
adding B to both sides you obtain A + B = X
When both numbers are negative, the behavior is as if you are dealing with positive numbers. For example, -5 subtracted from -5 is -10. It is essentially adding them, then adding on the negative sign.
