Did you know that the Russian passive construction (был сделан, будет сделан, the verb быть in the past or in the future and the short form of the past participle) is normally used in written and formal speech? In the colloquial speech we normally use the verb in the past or in the future (3rd person, plural, они) instead.
Задание было выполнено ими. The task was accomplished by them. Passive construction, formal or written speech.
Они выполнили задание. They accomplished the task. Active construction, informal and colloquial speech.