how d you turn the roman numeral number DCCXXXI into a regular number?

Answer 1

Start with the numeral on the left -- D which is 500.
C = 100 -- so there are two hundreds = 200
X = 10 -- three tens = 30
I = 1

500 + 200 + 30 + 1 = 731

This site has a great explanation.

http://www.yourdictionary.com/crossword/romanums.html