Romans used another system of numbers, very difficult to do any math calculations with, and missing the concept of zero. The Arabic numerals we use today successfully replaced the unwieldy Roman numerals.
roman numarals are v,i ,x,c and some other stuff with represent numbers
XII
in roman X
Your answer is XXI
L
538
CCCLXII
1 = I
XII
DCC
CXXVI
XXXIX