Assuming you are referring to Offset binary: https://en.wikipedia.org/wiki/Offset_binary, of which the most famous example would be Excess-3: https://en.wikipedia.org/wiki/Excess-3, then the solution would be:
- a) 77 + 127 mod 256 = 204 mod 256 = 204 = 11001100
- b) -42 + 127 mod 256 = 85 mod 256 = 85 = 01010101
etc…