советском

советском

"Советском" means "Soviet" (adjective, relating to the Soviet Union).

Here, 'советском' is used as an adjective in the prepositional case, describing 'союзе' (union) to mean belonging to or of the Soviet era.

В советском союзе была мощная экономика.

In the Soviet Union, there was a strong economy.

'Советском' modifies 'времени' (time) in the prepositional case, portraying the period as attributed to the Soviet era.

Многие фильмы рассказывают о жизни в советском времени.

Many movies describe life in the Soviet times.

'Советском' is modifying 'учебнике' (textbook) in the prepositional case, indicating the era or style of the textbook.

В моём советском учебнике были интересные задания.

In my Soviet textbook, there were interesting exercises.