Choosing 6 letters out of 10
I missed the lecture about this subject so now i need some help with this problem. (sry for my bad english, it ain't my nativ language).
I have 10 bricks with the letters [B],[E],[R],[N],[T],[B],[E],[R],[N],[T]
So in how many ways can i choose 6 out of this 10?
And [B][E][R][N][T][B] and [B][E][R][N][T][B] when the two b's have switcht places is counting as the same sequence of letters and shud not be counted twice. And that goes for all duplicates were 1 letters is choosen that another allredy have been on.
Whud be realy greatful for your help, i realy need to understand this to our upcomming eximination.
And if you dont know what i mean tell me and i will try to reply with a bether explanation.