Knowing this first, that there shall come in the last days
-2 Peter 3:3-5
One who scoffs at God's Word.
Jehoiachin was eighteen years old when he began to reign, and he reigned in Jerusalem three months.
-2 Kings 24:8
Jehoiachin was eight years old when he began to reign, and he reigned three months and ten days in Jerusalem:
One who takes God's Word seriously.
The God-hating scoffer often attempts to use Chronicles & Kings side-by-side, being willfully ignorant of the difference of testimony between the two books. However, worse than that are the typical leavened "ministries" that attempt to answer this as a "copiest error" in a lazy fashion that helps them justify their new-age bible versions full of errors, instead of going to the Word of God to find more details.
Jehoiakim was twenty and five years old when he began to reign, and he reigned eleven years in Jerusalem: and he did that which was evil in the sight of the LORD his God. Against him came up Nebuchadnezzar king of Babylon, and bound him in fetters, to carry him to Babylon. Nebuchadnezzar also carried of the vessels of the house of the LORD to Babylon, and put them in his temple at Babylon. Now the rest of the acts of Jehoiakim, and his abominations which he did, and that which was found in him, behold, they are written in the book of the kings of Israel and Judah: and Jehoiachin his son reigned in his stead. Jehoiachin was eight years old when he began to reign, and he reigned three months and ten days in Jerusalem: and he did that which was evil in the sight of the LORD. And when the year was expired, king Nebuchadnezzar sent, and brought him to Babylon, with the goodly vessels of the house of the LORD, and made Zedekiah his brother king over Judah and Jerusalem.
-2 Chronicles 36:5-10
So Jehoiakim slept with his fathers: and Jehoiachin his son reigned in his stead.
-2 Kings 24:6
Jehoiachin was eighteen years old when he began to reign, and he reigned in Jerusalem three months. And his mother's name was Nehushta, the daughter of Elnathan of Jerusalem.
-2 Kings 24:8
We also notice that both accounts say Jehoiachin's reign lasted three months, and this is because he only reigned solo over Jerusalem for three months (and ten days). Official timings for the throne of Jerusalem are only accredited to one person at a time, therefore, from 8-years-old to 17-years-old, Jehoiachin's reign was counted as a part of the time of reign of his father, Jehoiakim.
It is also interesting to note that the phrase "king over Judah and Jerusalem" was not used until 2 Chronicles 36:4 after Egypt's involvement.
And the king of Egypt made Eliakim his brother king over Judah and Jerusalem, and turned his name to Jehoiakim.
-2 Chronicles 36:4
Now in the eighteenth year of king Jeroboam the son of Nebat reigned Abijam over Judah. Three years reigned he in Jerusalem. And his mother's name was Maachah, the daughter of Abishalom.
-1 Kings 15:1-2
Though the Bible is not specific on exactly what Jehoiachin reigned over at the age of eight, based on these prior verses, it is most likely that he was given authority over Judah in essence (though Judah and Jerusalem's thrones were being combined into one), while Jehoiakim reigned in the main seat over Jerusalem. It wasn't until Jehoiakim died that Jehoiachin reigned in Jerusalem, and that helps us better understand the awkwardness of the situation, authority changing from Israel, to Egypt, and then to Babylon, all in a few short years in the early life of Jehoiachin.
In addition to this, 2 Kings also mentions the wives of Jehoiachin:
And Nebuchadnezzar king of Babylon came against the city, and his servants did besiege it... And he carried away Jehoiachin to Babylon, and the king's mother, and the king's wives, and his officers, and the mighty of the land, those carried he into captivity from Jerusalem to Babylon.
-2 Kings 24:11-15
Many new-age bible versions put in footnotes that say the Hebrew manuscripts do say eight in 2Ch 36:9, but they change it anyway. The change creates a problem because the Bible tells us:
Jehoiachin was eighteen years old when he began to reign, and he reigned in Jerusalem three months... And he did that which was evil in the sight of the LORD, according to all that his father had done.
-2 Kings 24:8-9