((MX))((M))Numerals in double brackets indicate multiplication by ten thousand and superscript numerals indicate multiplication by that particular numeral.Therefore:((MX))((M)) =...
http:/www.novaroma.org/via_romana/numbers.html
You can use the purple handy roman numeral converter on the side of the page.
Another contributor's answer:
XXX=30, XL=40, L=50, LX=60, LXX=70,...