Binary Subtraction

Let X and Y be numbers $X+Y$ is addition… right yes $X-Y$ is subtraction $X+(-Y)$ is also subtraction!

Now the question is, how can we represent a positive Y as a negative number, assuming we have some input… eh lets call it $C$, that determines if Y is negative or not? The answer: 2’s complement

So get the 2’s complement of Y and add it. That is all!