Best Answer - Chosen by the Asker
Depends of lots of things:
- Language the person wants to learn
- Language(s) the person already knows
- How well the person knows these languages
- Age of the person
- How much he works a day
- Motivation
- Health
- Memory, intellectual skills
- Whether these hours of study is studying lists of grammar or conjugation by heart (kind of pointless), or if these hours is serious practice
These are just a few I think =) I really don't think you can give an amount of hours. For one person, it could take 1000 hours, when for another person it could take 20000 hours.