Read these examples and identify the case before reading the explanation.
خَرَجَ رِجَالٌ. — Men went out. رِجَالٌ is a nominative subject with ḍamma.
رَأَيْتُ رِجَالًا. — I saw men. رِجَالًا is an accusative direct object with fatḥa.
مَرَرْتُ بِرِجَالٍ. — I passed by men. رِجَالٍ is a genitive noun with kasra.
Check yourself
Does being plural change these particular signs? No. It is a fully declinable broken plural in the book's first class.