The short answer is they should be IC but in accordance with today's rules governing the Roman numeral system 99 is notated as XCIX.
But 9*11 is the equivalent of IX*XI which works out as -XI+CX=IC (-1+100=99)
In fact the Romans themselves would have worked out the problem on an abacus counting device as LXXXXVIIII and probably simplified it to IC in written form because the Latin word for IC is 'undecentum' which literally means one from a hundred.
In todays modern notation of Roman numerals they represent 99
49.5 = SL in Roman numerals
99
The Roman numerals X-XCIX represent 10-99
99
The number 49 in Roman numerals is XLIX and the number 99 in Roman numerals is XCIX
The number 99,989 can be represented by the Roman numerals (XCIX)CMLXXXIX
The number 99,989 can be represented by the Roman numerals (XCIX)CMLXXXIX
99+1056 = 1155 or MCLV in Roman numerals Today we write out 99 in Roman numerals as XCIX but the Romans themselves would have probably wrote it out simply as IC (-1+100 = 99)
C=100 X=10 I=1 So it is 10 before 100 (=90) plus 1 before 10 (=9) . Thus the answer in ARABIC numerals is "99", while of cause XCIX in ROMAN numerals is "XCIX"
XCIX - XIX = LXXX
XCIX is the modern standard for 99.