Going back to school in the fall means getting a fresh batch of textbooks, which are always better used than new because other students have had the chance to doodle snicker-worthy stuff in the book.
These secret acts of vandalism used to be the funniest pictures in textbooks (unless you had a book from the 50s or 60s which was full of outdated information), but nowadays LOL-worthy stuff is included on purpose.
Okay, that one was obviously a mistake they missed during editing, but this picture must have been included on purpose, right?
Maybe it's for "Geometric Racial Stereotypes: a journey in racist maths"? They're teaching some strange stuff in schools these days...