Achoir has 3 spots open for altos, and 8 altos are interested in them. in how many ways can the open spots be filled?

Since order is not important for unique combinations, we need to apply the "n choose k" formula

n!/(k!(n-k)!), n=number of elements to choose from, k=number of choices made

In this case:

8!/(3!(8-3)!)

56

So there are 56 unique threesomes possible with 8 members.