Nobody did/
Different people find different things difficult. So what you might find difficult someone else might find easy. And, what someone else finds difficult, you might find easy. As a result, there is no hardest type of mathematics and so nobody could have invented it.
The Collatz conjecture
what is the percentage of the gods existence in this world ? its 23846.63542
It really depends on who you're asking....
Anyone can if they work hard at it.
I assume you mean "whole world" rather than "hole world". There is no "hardest math question" because one's field of knowledge may be different to another. Therefore, the hardest question for one person may be an easy one for others.
No. Some of the world's hardest maths problems have remained unsolved for centuries.
What is hard for some people may not be hard for others. So there is really no answer to this question.
Foucault's last conundrum.Fermi's last theromExact value of Pi.
n+1=n solve for n.
math
The hardest question is too difficult to conjure.
Prove that 2 <> 2. Show your working.