logic puzzle?

According to your rules, if there is a vowel on one side then it HAS to have an even number on the other, and every card HAS a vowel on one side, that means that card b and card d do not follow the rules because you couldn’t have a consonant and an odd number, unless one assumes that there could be more than one letter and one number on each card.

This is the only conclusion one can reach from the facts given.

So one would have to turn over a and c to find out if the rules have been followed.

Turn over card b) with letter T. If the other side is a vowel, then the rule is broken, since the letter ‘T’ is not an even number. If it is not a vowel, then the rule that “one side must be a vowel and the other side a letter” is also broken.

I believe that you need to turn over Card A to confirm that the card that is known to contain a vowel does indeed have an even number on the other side.

Card B has a consonant. THere is no rule for a consonant so the number on its reverse side is irrelevant.

Card C has an even number, but the rule does not state that all even numbers have vowels on their reverse. The rule applies only when you know that there is a vowel on one side.

Card D is an odd number, for which no rule is stated.

The rule says nothing about consonants and/or odd numbers so cards b) and d) can be ignored. The rule says if one side is a vowel, the other side must be even, BUT it does not say that if one side is even the other side can’t be a consonant. Therefore, card a) must be flipped to determine if the rule has been broken.