How do I add, subtract, multiply and divide roman numerals?

MMM       CM             XC                    IX               +

M                       CC                XXX               IV

-------------------------------------------------------------

MMMM    CM    CC   XC        XXX     IX      IV                  

MMMM      M       C     C           XX     iX       IIII

MMMMM                CC              XX      X       III

MMMMMCCXXXIII

\(\bar VCCXXXIII\)

I just lined them up and did it a bit like algebra then I took the minus units away from the plus units etc.  

It was an interesting exercise that I had not done before. 

WollframAlpha actually is capable of performing these operations.....I suppose there are some algorithms that one could learn, but....I'm not sure it would be worth the trouble to remember them !!!

Just for fun...here is the answer to the third one :

B TW...the last one can't be represented by a Roman Numeral....it produces a decimal approximation

MMM       CM             XC                    IX               -

M                       CC                XXX               IV

-------------------------------------------------------------

MM       (M-CCC)    (C-XXXX)         (X-I) -(IIII)

MM     ( DD-CCC)     (LL-XXXX)           V

MM         DCC                LX                   V

MMDCCLXV