I am solving this equitation, looking for the output based on given input. I've been told by one mathematician this can be solved using Extended Euclidean algorithm, but dunno how, anyone (@_peter_ r?) kind to help, please? BTW, this is Wolfram Alpha solution:

you need to solve modular Inverse of (0x2a29,0xfff1) getting the ModularInverse you can solve it ModInv(a,b)*Input mod b but remember to obtain a valid solution a and b needs to be coprime!!

@RoOkiE JoeY, WOW! Thank you very much, I am impressed, thank you for an explanation. Can you share gRn Rsa-Donkey, please?

let's get the basics first btw rsa-donkey 1.2.2 beta is on the net but only covers rsa (you won't find above calculator tab)

@draww indeed basic are fundamental. Yes the RSA-Donkey 1.2.2 was released few years back on exetools board but there was no feedback so the project was stopped, in the meantime we added few things that can become handy when dealing with such stuff.