I need 3 different names for the number 15 and 999

Answer 1

simple: translate

nine hundred ninety-nine into three languages...
negenhonderd negenennegentig in Dutch

then translate fifteen into three languages.

http://babelfish.yahoo.com/translate_txt

Answer 2

fifteen,10+5,5*3=15.nine houndered,ninety nine,900+90+9,333*3=999