You can view digitized versions of the problem book at the Russian National Library or NLR Digital Library to check if your version matches the latest editions.
Identify which variable you have (e.g., ) and which one you need ( You can view digitized versions of the problem
Searching for a for "Problem Book in General Electrical Engineering with Fundamentals of Electronics" edited by T.F. Berezkina can be tricky because a single official "answer key" book for every edition doesn't exist in a traditional sense. However, the textbook itself is designed to be self-sufficient for students. Why You Might Not Need an External GDZ You can view digitized versions of the problem
Sections end with questions and problems for independent study to test your comprehension. You can view digitized versions of the problem