Equations which link values of variables in various moments of time are called difference equations (recurrent relations). Even though it is much easier to construct models using difference equations, scientific researchers usually apply differential equations. It is probably due to the fact that differential equations are more explored in scientific and academic books. Desire to make up the deficiency is the main reason for writing this book. A distinguishing feature of this work is the availability of many different problems, examples and situations. A scientific value of this book is identified by the new methods of solving linear difference equations proposed by the author. Studying this book is going to be useful for not only those who analyze different economic situations, but also for the analysis of problems associated with ecology, social sciences and so on. At the same time, it doesn't take special background knowledge in order to study the book. Despite having covered a wide range of problems, most of the materials are available, and we hope is going to be interesting, even for high school students.