Fermat's Last Theorem is one of the most famous mathematical conjectures in history, first proposed by Pierre de Fermat in 1637 and left unsolved for 358 years until finally proven in 1995 by Andrew Wiles. The theorem states that given the equation an + bn = cn for any integer n > 2, it is impossible for a, b, and c to all be integers.
In the anime, the player is given five seconds to answer each "Quiz Action" card, which for this card would be impossible by any reasonable standard; Wiles' proof took seven years of work on top of untold decades of other mathematicians' work before him who tried and were unable to complete it. Even if one somehow were to memorize (let alone understand) the entire proof, it requires over 100 pages to write down and a specialist to even read.
By contrast, in the English dub the question simply asks for the first 100 digits of the number pi, which is (comparatively) much more straightforward to memorize and has been done by several people. However, it would still be effectively impossible to read them all in five seconds.