This video clearly explains how to perform binary addition and subtraction. Binary addition is a simple process and binary subtraction needs a little bit of more thought.
1+0=1
1+1=0 (With a carry of 1)
0+0=0
And the subtraction goes like this:
1-0=1
1-1=0
0-1=1 (With a borrow of 1) - This logic is also explained in the video.