Wonder wall - How do Roman numerals work

Hello everyone! Room 32 are creating a Wonder Wall. For homework we had to make up some questions for it and research one of them. Here is how Roman numerals work.

Key: I=1 V=5 X=10 L=50 C=100 D=500 M=1000

If the letters repeat more than once it means that to multiply it that many times. e.g. XXX=30 and CC=200. If you repeat a letter, it may only be repeated three times or less. If one or more letters are placed after another letter of greater value, you simply add them. If it is the other way around you subtract. e.g. VI=6 and IV=4. Only subtract powers of ten - 10, 100, 1000 etc. Only subtract one number. A bar placed on top of a letter or a string of letters, increases the number by 1000.
Some examples:
MCCXI = 1211
CXXII = 122
MMMDVII = 3507
DCCXCVIII = 798
These four examples clearly show that this method is not the most efficient way of writing numbers. Imagine having to multiply or do other mathematical processes with these Roman numbers!That is why we do not have Roman numerals; they are much too complicated to do in an IKAN or something of that sort.