How to clear my system of THC?

I've finally been hired. With the holiday weekend coming up, it'll take about a week for my background check to go through. Then I got drugged test immediately after. I smoked Saturday night. Please, no lectures! It was my first time ever, and it was incredibly bad timing. By the time I get tested, it'll have been about 10-11 days. Having that in mind, and that it was only one time, what can I do to clear my system of the THC? I'll buy anything if it's necessary, but I'd rather not. I don't know if it's relevant or not, but I'm 16 and about 100 lbs. Also, I don't know if it's a saliva or urine test. Thanks so much.