I am familiar with the concept of subtext, thanks. I think you've mistaken that what is incumbent upon you here is to demonstrate what subtext has been contained within the text as you put it, in either the OP or my example, that was missed.
I mean in the case of my old school memory I think you'll just have to indulge my recollection that there was none (in fact, that all subtext in that situation related to being in math class etc purposefully indicated that it was a genuine math question, by the teacher's design). But in the OP greentext parable, literally some text presented devoid of context, which actually is relevant in that it establishes that there is a closed loop of literary conventions in that text which can be analysed or 'comprehended' - what is the subtext?