Well.....you're probably not "stupid'..it required some level of intelligence to find your way here, didn't it??...you just might know the answer to this question.
Remember........a man is considered wise if he admits he doesn't know something...
Well....enough of my pearls of wisdom
The answer is 15! = 1,307,674,368,000
The "!" is known as a "factorial'
Let me give you a simpler example of this......Suppose we had three books on a shelf and we wanted to know how many different ways we could arrange them. Well, we have:
(3 ways to select the first book) x (2 ways to select the second book) x (1 way to select the last book) = 3 x 2 x1 = 3!
So, you can extrapolate this to your basketball roster by
15 x 14 x 13 x 12 x..........x 3 x 2 x1 = 15!
And that's it......Good luck to you...