Can I Pass A Drug Test If I Havent Smoked Weed In Three Weeks?

By "Smoked", I am assuming you mean marijuana.  Marijuana stays in a single time users system for approximately 2-3 days.  If you are a chronic user it could stay in there for up to 2 months.  If it really was once you should be good but if it was more than I would be careful.  Synthetic urine or  detox packs can be found online.  Cranberry Pills also work well, can be purchased at any drug store.  Good Luck

Can be detected for 30 days

Yes if you dilute your urine with water 2-3 hours befor the test.

You better give it 1 more week as it usually takes 30 days to get out of your system.

Usually takes 30 days to get out of your system so give it about 1 or 2 weeks