"Let X equal a crocodile" is a book from a series of educational and cognitive literature for children. In this book, the author not only teaches children mathematical concepts, but also uses these concepts to create exciting and interesting adventures. Together with the main characters of the book, children learn numbers, addition and subtraction operations, and also learn to think logically and solve problems. This book not only helps children acquire mathematical knowledge, but also promotes the development of imagination, logical thinking and creativity. Thanks to bright illustrations and an exciting plot, "Let X equal a crocodile" will become a favorite material for learning mathematics for every child.