I can play 3:2 1/4, 1/8, 1/16 note triplets because I hear them used all the time, and can just play it without actually counting it out, i just know how it sounds.. Is
 it possi
 ble to be able to sight read these kind of weird tuplets/polyrhythms? Or is it something that you just have to hear each particular rhythm over and over again until it sinks in?
no matter what year you live in or what country you go to, these types of complex mathematical exercises will be used in less than 1% of music. most often when complex number tuplets are used, (5, 7, etc) it is really only an approximation of something else, more musical perhaps. always check with the director or composer because they might be able to describe what they are looking for