Let's learn by an example:
CIX + CV + CCCXL = ?
109 + 105 + 340 = ? The Romans did not have the Hindu-Arabic numbers
1. Substitute for subtractives.
Substitute for any subtractives in the roman numerals; that is, "uncompact" them using only the additive notation.
Subtractive notation = a group of two numerals, one of a lower value preceding another larger one, the only allowed ones are: IV, IX, XL, XC, CD, CM, M(V), M(X), (X)(L), (X)(C), (C)(D), (C)(M) - to calculate the value subtract the first symbol from the second.
Additive notation = a group of two or more numerals, equal or sorted in descending order from high to low, largest symbol on the left, down to the smallest on the right - to calculate the value add up the symbols.
IX = X - I = V IIIII - I = V IIII = VIIII
CIX = CVIIII
XL = L - X = XXXXX - X = XXXX
CCCXL = CCCXXXX
2. Put the Roman numerals of the same sign together.
3. 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.
4. Combine groups of the same symbols together.
Starting on the right end (smaller values), combine groups of the same symbols into larger ones.
5. Rewrite the repetitive symbols.
Rewrite the symbols written in excessive additive notation by using the substractive notation.
The numeral I should not repeat itself more than 3 times in a row, rewrite: