Right, as we all know, the most sensible way to do nonary algebra is in ternary, so we simply calculate 22+21 and convert back to nonary, and optionally decimal afterwards. So, 2 add 1 is 0, carry the 1, add it to 2 for 10, add the 2, carry the one, pad to 4 places and we have 0120, or 16 in base 9. Now to convert to decimal... removes shoes and socks