I found my wallet.dat in my old computer. but i dont remmember the key and passord. Anyone can help me. I will pay 15%
Which "key" are you talking about?
If you don't know the password, you'll have to bruteforce it.
Depending on the length and complexity of the password this either is a possible or impossible task.
The more you know about the password, the better your chances are. Unfortunately you gave us very little information, so we can't really say anything else.
If you however bought the wallet file, then you got scammed and the wallet does not contain any keys and therefore no bitcoins can be retrieved.