The workbook by Verbitskaya is another staple with available solutions online.
This workbook by Vaulina and Dooley is widely used. Sites like Gdz.ru provide page-by-page breakdowns of every module, from "Family Members" to "Festive Time". gotovye zadaniia po vork buk angliiskii iazyk 6klass
If you use the Afanasyeva and Mikheeva series, you can find complete answers for both the standard and advanced tracks on Gdz.ru. The workbook by Verbitskaya is another staple with