Kumon Math Level N Solution Book 〈LEGIT〉

I'm assuming you're referring to the Kumon Math Level N solution book. Here's some information:

Kumon Math Level N is a advanced math level in the Kumon Mathematics Program, designed for students who have completed Level M. At this level, students review and master advanced algebra, functions, and graphing, as well as develop an understanding of mathematical concepts and problem-solving skills.