I just forgot to put odd there is all. Should read "turn over a card with an odd number on it." You can prove the rule, because as long as a vowel is always opposite an even number, you're good to go. The only other card you need is the 9, because it will tell you if the rule is true or false by whatever its opposite is. If it's a vowel, the rule is false. If it's not, the rule is true. You can then infer that the rest of the deck follows this rule.
Agreed; and now I see what you're saying.
I was misled because I was using the words "prove" and "verify" as different things, whereas you were using the word "prove" in the sense I was using the word "verify". Frickin' semantics!
I'm probably not using the words correctly in a mathematical sense. I was just trying to explain the problem the way I knew how. I'm taking Finite Math in the Fall, so I should probably brush up on the correct terminology. Oops!