can you pass a drug test if you smoked for 3 days and the drug test was in 29 days?

Answer 1

I assume that you're talking about Marijuana here.
That's actually pretty problematic, the thing is that THC (the active substance in Marijuana - it's the part that gets you stoned) is fat soluble, so it has a tendency to hang out in your body for a while. Now, for one time, it usually lasts a few weeks at most (that's usually, it's impossible to predict for a given person), but with regular use, it can stay around in detectable levels for months, so if you've been smoking a lot, you may be in some trouble.
For more specific information, you can poke around at
http://www.erowid.org
it's a good site for finding out pretty much anything you would want to know about any psychoactive substance.

Answer 2

possibly but don't count on it