جَاءَ أَحَدَ عَشَرَ طَالِبًا — Eleven students came.
جَاءَ: past verb built on fatḥ.
أَحَدَ عَشَرَ: compound numeral, both components fixed on fatḥ, in the nominative position as subject.
طَالِبًا: accusative numerical specification (tamyīz).
Why: Do not change the numeral to «أَحَدُ عَشَرُ» because it is a subject. Its fixed endings do not prevent it from having a nominative syntactic role. This sentence is an instructional addition.