In combinatorics, this question is a combination question, because combination deals with selection while permutations deal with arrangement.
[tex]nCr = \frac{n!}{(n - r)!r!} \\ [/tex]
Plugging in our values,
[tex]8C3 = \frac{8!}{(8 - 3)!3!} = \frac{8!}{5!3!} = \frac{8 \times 7 \times 6 \times 5!}{5!3!} = \frac{8 \times 7 \times 6}{3 \times 2} = 56 \\ [/tex]
That means 3 desserts from a tray of 8 desserts 56 times.