Following are a number of back-translations as well as a sample translation for translators of 2 Kings 11:21:

• Kupsabiny: “Then he took the commanders, the guards of the house of the king, the other guards and all the common/lay people and made them escort the king. They left the House of God and passed by the gate of the guards up to the home of the king. Then Joash sat down on his chair of rulership. He had/was at that time seven years (of age).
  So, all the people of Judah were happy and then peace came to the city of Jerusalem because Athaliah had been killed.” (Source: Kupsabiny Back Translation)
• Newari: “Joash was seven years old when he became King of Judah.” (Source: Newari Back Translation)
• Hiligaynon: “Joash was seven years old when he reigned in Juda.” (Source: Hiligaynon Back Translation)
• English: “Joash was seven years old when he became the king of Judah.” (Source: Translation for Translators)