'Eighteen' in the Bible

Jehoiachin was eighteen years old when he began to reign, and he reigned three months in Jerusalem. The name of his mother [was] Nehushta daughter of Elnathan from Jerusalem.

The height of the one pillar [was] eighteen cubits; a bronze capital was on it, with the height of the capital [being] three cubits. The latticework and pomegranates on the capital all around were bronze, and likewise on the latticework for the second pillar.