1. Simplify the operation.
Cross out the common symbols in the numerals of different signs.
Matching numerals / symbols are colored the same.
CCXLIX - XIII + CXXV =
CCXLIX - III + CXV
When crossing out,
do not mix subtractive and additive groups symbols:
for example ...
2. Substitute for subtractives.
Substitute for any subtractives in the roman numerals; that is, "uncompact" them using only the additive notation.
Subtractive notation, additive notation: more information ...
XL = L - X = XXXXX - X = XXXX
IX = X - I = V IIIII - I = V IIII = VIIII
CCXLIX = CCXXXXVIIII
3. Put the Roman numerals together, as a string.
Catenate the positive numerals together:
4. Sort the symbols in order.
Sort the symbols in order from left-to-right with the largest symbol on the left, down to the smallest on the right.
Sort the symbols of the positive numerals:
5. Cross out (remove) any symbols occurring in both strings.
6. Combine groups of the same symbols together.
Starting on the right end (smaller values), combine groups of the same symbols into larger ones.
CCCXXXXX XI =