As a teacher, Subroto has seen a lot. This thickly bespectacled man has been teaching mathematics at junior high school level (SMP) for 38 years. So it’s not difficult for Pak Broto – as he’s called by his students – to discover ridiculous mistakes in one of the compulsory mathematics textbooks distributed by the Ministry of National Education. "As an example, it is said that a square can be put in its frame four times, wh...