Q103: Number 14 is it?

In Land of Black Gold a Calculus invention is named "formula fourteen", but where do we see "X.14"...?

No need for page numbers, just describe the scene and tell which book it's in. It is ok with page number if you prefer that, what ever works fine.

And Yamilah, please give the others little more than three minutes this time.

Over 120 minutes (= 40 times 3 minutes!) have passed; am I allowed to try and answer now?
As far as I remember, X.14 is the signature on the document that wrongly accuses Tintin of spying for Nuevo Rico, in The Broken Ear (p.35-B2).
Is that what you meant, labrador road 26?

Give or take a minute or two, and you will always get it right. Yes Yamilah you score again. I bet you used your secret powers again. Well it's your turn, as always.