Let b056e0e6a45a7e57ed4ea9f6285" title="Click to view the MathML source">Zn be the ring of residue classes modulo n , and let e5b7160a0faa38229"> be the group of its units. 90 years ago, Brauer obtained a formula for the number of representations of 8bd3a328f5e4695a6eeda9c7ee5f2fe9" title="Click to view the MathML source">c∈Zn as the sum of k units. Recently, Yang and Tang (2015) [6] gave a formula for the number of solutions of the equation b9069d5f507187f31bcb96023e2"> with e6e96a11696">. In this paper, we generalize this result. We find an explicit formula for the number of solutions of the equation b91091be5bfb5a3d"> with b2b18e002673d82cd4f">.