CREATE TABLE table_50518 ("Nominative" TEXT, "Ergative" TEXT, "Dative" TEXT, "Genitive" TEXT, "Instrumental" TEXT, "Adverbial" TEXT)

What instrumental has tkven-i as the genitive?
SELECT "Instrumental" FROM table_50518 WHERE "Genitive" = 'tkven-i'
SELECT "Instrumental" FROM "table_50518" WHERE "Genitive" = 'tkven-i'