Tamara G. Stryzhak researches the stability of solutions of the system of linear difference equations with random Markovian coefficients. She also deals with Lyapunov functions which were used to receive the necessary and sufficient conditions of the stability of the solutions in the average quadratic mean. As an example, Stryzhak discusses the stability of solutions of a single difference equation with one random Markovian coefficient which takes on two values. The series on Modern Mathematics for Engineers is addressed to upper-course University students in Mathematics specialties, to graduate students and to researchers who apply Mathematics in different spheres.