Why is it that the “number of ways that we can get an odd prime three times when a die is rolled five times” is 10! over 3! x 2!? Can someone explain it a little more for me? thanks! i understand the rest of the solution

5! not 10!

Yeah, sorry I meant 5!. But why is it 5! over 3! x 2!? I don’t get how this combinations is calculated

Recall that combinations (\binom{n}{r}) (i.e, not permutations) is

\binom{n}{r} = \frac{n!}{(n - r)! r!}

Does that help?