This is a set of teaching materials distributed to students in the second-year (high school) second semester regular math course at Teru-ryokukai. The first textbook on the left is unused, but the second and third textbooks from the left have some writing in them with a mechanical pencil, as shown in the 3rd and 4th photos. It's perfect for tackling as a countermeasure for areas that third-year students struggle with.