Yes, it is a common practice of textbook authors and publishers to include study questions and answers to those questions, either in a key at the back of the book or within the text.
Where and how the study questions and answers are included depends greatly on the type of textbook and on the publisher. For instance, mathematics textbooks typically contain a multitude of practice questions, though the answers at the back of the book of student editions may only contain answers to the odd-numbered problems. Teacher editions of current textbooks contain answers to all practice questions, as well as additional learning resources. Older editions of textbooks may or may not have the same amount or types of questions, as textbooks are constantly being updated and edited to reflect new and evolving information and best practices. Many textbook publishers have created online sources to supplement the information in the textbooks used by students world-wide.