XX is 20 in Roman numerals
20 = XX
you write 71 as LXXl and 20 as XX
Xx, xxi, xxii, xxiii, xxiv, xxv, xxvi, xxvii , xxviii, xxix, xxx
XX
XX.VI.MCMLXXVI
II.XX.MMI
I-XX-MMIX
It is: I-XX-MMI
Xii-12 xx-20 mcmxc-1990
X-XX-MMIII
83 = LXXXIII or as XXCIII (103-20)
V-XX-MMX