XX is 20 in Roman numerals
20 = XX
you write 71 as LXXl and 20 as XX
XX
XX.VI.MCMLXXVI
II.XX.MMI
I-XX-MMIX
It is: I-XX-MMI
Xii-12 xx-20 mcmxc-1990
V-XX-MMX
83 = LXXXIII or as XXCIII (103-20)
X-XX-MMIII
825 as a Roman numeral is DCCCXXV meaning 800+20+5 = 825