Question

9+10 equals 21 is correct 9+10 in roman numerals are true IX+X=XXI?

Answer 1

9+10=19 not 21
and in roman numerals IX+X equals IXX because if you put the "I" in front of the "X" it means that the number is 1 less than the value X ("X" in roman numerals equals 10 and "I" equals 1). Also if you put the "I" after the "X" it means that the value of that roman numeral is 1 more then "X".

Answer 2

Not if you keep the ' l ' before the ' XX ' where it belongs. If it's before, then it means take the ' l ' away from them, and you get 19 just as you should. Now I understand this crazy question that keeps coming around.