See sibling threads.

Short version:

You are presented with 4 cards on a table. You can see one side of each card.

You are told two things:

1) Each card has a number on one side and a color on the other side.

2) If a card has an even number, then its color is blue.

It is not unreasonable assume that you are expected to verify all things you have been told (i.e. all things you cannot verify by what you observe).

Since you know you can't trust the second thing you are told about the cards, why should you assume that the first thing you are told about the cards is true?

OP is saying that you cannot trust anything you've been told, and is attempting to verify (2) without trusting (1). I misinterpreted and assumed that OP was saying the goal to verify all statements that you've been told.

No, you're told these things:

1) Each card has a number on one side and a color on the other side.

2) Pick the minimum numbers of cards needed to verify the statement "If a card has an even number, then its color is blue".

>Since you know you can't trust the second thing you are told about the cards, why should you assume that the first thing you are told about the cards is true?

This reading doesn't make any sense. If you were indeed given (1) and (2) in that form, and indeed couldn't trust them both, then there would be no quiz at all. Just 2 random sentenses that might or might not be true.

In the setup, you are presented with four actual cards in front of you, two where you can see a number, and two where you can see a color. This is verifiable with your senses. You are then told two statements about these cards and asked to verify the second statement.

As OP of this thread pointed out, the card with 5 must be checked, because it's possible that it has an even number on its reverse side.

I originally misinterpreted the OP as saying that both (1) and (2) must be verified. You can see the two sibling branches that explore both of these in much more depth and back and forth.