[Two houses with an x]

I think most around here will know the answer to the house with the x in the middle, which you have to draw with one line, but there also is a puzzle in which you have to draw two of them next to eachother in one line. Is this possible? And if not, can you prove why it isnt possible?

[9, 99 or 999?]

There are no comma's in the numbers themselves

[9, 99 or 999?]

But If the number would be 9 or 999, the answer to your question would be 'no'. So you would only find out if the number is 99

[9, 99 or 999?]

I am thinking about one number, it's 9, 99 or 999. You can ask one question to me on which I can answer yes or no to find out what number I'm thinking of. What question do you have to ask?

Anyone know the answer?