The official answer to this puzzle makes a huge assumption: that there is one correct answer. There is not one correct answer. (x, 2x, 4x) gives you a "yes" every time, therefore it is a correct answer, at least as automatically checkable, and there's an infinite number of such tuples. To find a "no" you're reduced to random guessing. That's not a puzzle, that's crap. The confirmation bias material might be true, but…
It's amusing that you went to a website on confirmation bias, did the puzzle incorrectly, presumably read the material on confirmation bias, but still suffer from the effects of confirmation bias.
Amusingly human, if I may add. Reading "Thinking, fast and slow", by Daniel Kahneman, one key idea that I got was that even knowing against biases you are very, very likely to suffer from those biases. Disheartening results were gathered from studies done on well-trained psychologists and people prepared for the experiment, to no avail. Can't remember the details right now, but just read the book, it's awesome. Another good one was "Influence" by Cialdini, but they gave you tips on trying to avoid those biases that, upon reading Kahneman, I don't think anymore that are very useful.