Euroki.org is useful for finding variations of the same exercise if your textbook version differs slightly.
The exercise usually requires students to complete sentences by inserting the correct case endings for nouns or analyzing verb conjugations. : Completing noun endings or verb analysis. Sample Solution (Noun Endings) : Euroki
Мой брат служит в (в чём? — П.п., 1-е скл., окончание -и). Euroki