Subtracting a two's complement value from another two's complement value I'm trying to solve the following problem: 

$$ 6AD3 - AF20 $$

Both of these are hex values in two's complement.

I keep getting one answer but it's turning out worng. What I tried to do, was take the complement of AF20, which I got as 50D1, and instead of subtracting, I added it to 6AD3, and I got BBA4, however, I am being told this is the wrong answer.

Where am I going wrong?
Converting 6AD3 to binary gives 0110 1010 1101 0011 (the division to 4's is just to make it readable)

Converting AF20 to binary gives 1010 1111 0010 0000
To complement the latter in two's complement, we take the bitwise negation (one's complement) and add 1.

So the one's complement is 0101 0000 1101 1111, and adding 1 gives us
0101 0000 1110 0000
Adding this to 0110 1010 1101 0011 we have:

0101 0000 1110 0000

+

0110 1010 1101 0011

=

1011 1011 1011 0011

Which is BBB3.