'Eighteen' in the Bible

Jehoiachin was eighteen years old when he began to reign; and he reigned three months in Jerusalem; and his mother's name was Nehushta, daughter of Elnathan of Jerusalem.

The height of one pillar was eighteen cubits, and the capital upon it was brass, and the height of the capital three cubits; and the network and the pomegranates, upon the capital round about, all of brass: and similarly for the second pillar with the network.