D
The letter "D" represents the number 500 in Roman numerals.
Because in ancient Rome I) meant 1*500 = 500 and (I) meant 1*1000 = 1000 and over time they became D and M respectively
16
LV
V
That is 29.
MCXVII
10 = X in Roman numerals
3409 in Roman numerals is MMMCDIX
DCCCXXXII in roman numeral is 832.
VI = 6
20