رَأَيْتُ الْمُعَلِّمَيْنِ فِي الْفَصْلِ.
Translation: I saw the two teachers in the classroom.
رَأَيْتُ: past verb with first-person subject suffix.
الْمُعَلِّمَيْنِ: accusative direct object with yāʾ because it is dual.
فِي: preposition.
الْفَصْلِ: genitive noun with kasra because it is a regular declinable singular.
Takeaway: Different noun classes can require different case markers within the same sentence.