This is the 2248th most frequent Russian word.
задачей
"Task" or "problem."
Used in the instrumental case indicating the role or function of 'task'.
Основной задачей компании является увеличение прибыли.
The main task of the company is to increase profit.
Used in the accusative case as a direct object to a verb.
Мы решаем каждую задачу с особым вниманием.
We solve each task with special attention.
Used in the prepositional case to indicate circumstances or context.