This is the 18455th most frequent Russian word.
эффективных
"Effективных" means "effective" or "efficient" in English.
In this sentence, 'эффективных' modifies 'методов обучения' and describes the attribute of being effective.
Я рекомендую вам использовать эффективных методов обучения.
I recommend that you use effective learning methods.
Here, 'эффективных' specifies the type of 'решений', indicating they have a quality that achieves desired results.
Для успешного завершения проекта требуются эффективных решений.
For the successful completion of the project, effective solutions are required.
In this case, 'эффективных' qualifies 'сотрудников', emphasizing their capability to perform tasks successfully.