How long does marijuana stay in your system?

I smoked a hit the other night. (first time in about 3 months) I don't think it was good stuff and I may have a drug test in about 3 weeks. Should I be ok? What about a hair test?How long does marijuana stay in your system?
Should be ok with piss test, drink alot of water between now and test time to flush out good. Hair test is not likely to pass as they can go back 6 months to a year. Good luck.
Marijuana stays in your system for about 2 weeks. Marijuana will stay in the fat cells, so if you are heavier, it can stay in your system for longer.
weed stays in your system for about 25 days at the most so if you just took one hit you should be ok.. If they do a hair test, they will be able to tell what kind of drugs you have done in the last 2-3 years.
Marijuana isnt water soluable, so all those myths about drinking water is not true, it stores in the fat. You taking one hit, you should be ok in 7-10 days...