If you can give an example I would know exactly what you mean, but normally it works like this.
When you have 3 and you want to add -1, you're actually subracting 1.
Imagine this in a number line.
< -3, -2, -1, 0 1, 2, 3 >
when youre at 3, and you want to add a -1, you're going to the left side, closer to the negatives.
Let's say you had 2, and you want to SUBTRACT -1.
Those two words cancel out: "subract" and "negative". Look at the number line again.
If I'm at 2, and I'm SUBTRACTING from the negative side, I'm moving it to the right side- I'm adding!
In an equation, 2- -1, the two minus signs next to each other like that cancel out, so you have 2+1 which equals 3.
That's pretty much it for adding and subtracting negatives. There's more for multiplying and dividing too.
