Presumably you mean in Roman numerals?
If so then the answer is VD but with an horizontal bar above the numeral V to indicate multiplication by thousand. So 5000+500 = 5500.
5000 is represented in Roman numerals by a 5 symbol, which is V with either a horizontal bar above it (which I can't show using my keyboard) or by a V enclosed in brackets = (V). 500 is represented...