Are you just copy pasting some homework? I read in 20s on Wikipedia and I already know how to do that.
I´ll try to explain it.
1+1= 0
1+0= 1
(a+b)+c = a+(b+c) (I´m not sure what the value of that would be here)
So for every line you add the value+key, following the rules. Example, the first line:
00010000
+
01010101
-------------
01000101
I´m pretty sure that´s right. Maybe someone can confirm.