The rule is given - you are not asked to infer any rule, only to confirm or deny the given rule.
You can confirm that the two cards you picked up conform to the rule but there are alternative systems of rules cause the two cards to be even and have vowels and not conform to the rules. You are told to "determine whether the following rule holds for the deck" and that "these four cards represent the rest of the deck." I suppose that you are supposed to infer that if "these four cards represent the rest of the deck" and if vowels on the cards are even than "the rule holds true for the deck." I just couldn't say that the rule holds true for the deck by turning up two cards, even if they conform to the rule, as long as there are other set of rules that could invalidate "all even numbers have vowel."