Well, "ternary" does mean base three, and base three is often used with a positional notation, but I don't know that it's required. Perhaps that's why jan kipo uses the term "triseimal", which, by context, I believe he means three digits (0,1,2) rather than base three.
And yes, any (Rational number) base numbering system can do the same math as binary or decimal. Base three has the interesting properties that 1/3 is a nonrepeating decimal number (0.1) whereas 1/2 is not (0.11111...)
https://en.wikipedia.org/wiki/Ternary_numeral_systemBut otherwise you can build a multiplication tables and do all common math as directly as with any other positional notation except in this case (below) you would start from the left.
nanpa mute ala tu (=6)
en
nanpa mute ala wan tu (carry the wan) (=21)
li
nanpa mute ala ala ala wan (=27)
(remember it's reversed)
02+
012=
0001
To multiply I would probably overload the operator "mute",
nanpa mute tu
mute
nanpa mute tu
li
nanpa mute wan wan.