Question 580374
There are 18 ways to choose the first person


There are 17 ways to choose the second person (since a single person can't be chosen twice)


There are 16 ways to choose the third person


There are 15 ways to choose the fourth person


There are 14 ways to choose the fifth person


There are 13 ways to choose the sixth person



Multiply these all together to get: 18*17*16*15*14*13 = 13366080



So there are 13366080 different ways assuming order matters.


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If order does NOT matter, then this means that you've been overcounting. To fix this issue, you need to divide by 6! = 6*5*4*3*2*1 = 720 to get


13366080/720 = 18564



So there are 18564 different ways assuming order does NOT matter.