Because this is an older textbook, physical bookstores specializing in used books (like Ozon) or dedicated, retro-education websites might have answers.
This is a classic Soviet-era, later Russian, textbook focuses heavily on botany (plants) for 5th and 6th-grade students. Where to find answers (GDZ): gdz po biologiia 5.6 klass korchagina
Based on your request, I found information related to the older, classic textbook: . Because this is an older textbook, physical bookstores