Comment by bufferoverflow

But how do you classify a question as high vs low complexity? Some seemingly simple questions can turn out to be very very complex. For example, integer solution to

    x³ + y³ + z³ = 42 

took over a hundred years of compute time to find.

Or another seemingly simple equation with positive integers x,y,z

    x/(y+z)+y/(z+x)+z/(x+y) = 4

requires elliptic curve knowledge, and the solution is huge

    x = 154476802108746166441951315019919837485664325669565431700026634898253202035277999

    y = 36875131794129999827197811565225474825492979968971970996283137471637224634055579

    z = 4373612677928697257861252602371390152816537558161613618621437993378423467772036

(Solution is discussed here: https://www.quora.com/How-do-you-find-the-positive-integer-s...)