Question: combinations

[EllieD497]

26 letters (a-z), 5 vowels, and 21 constants. If we choose three different numbers at once, how many groups include 2 or more vowels?

[RonPurewal]

Hello,

Per the forum rules, we need a citation of the original source of the problem. (Original authorship--not another forum or other secondary source.)

Also, you might want to check the wording of the problem, as it's currently self-contradictory. (The question is framed in terms of letters, but then you're talking about choosing numbers.)

Thanks.