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
Your answer is XXI
L
1 = I
538
CCCLXII
XII
XXXIX
DCC
in roman X
CXXVI