The term of office of the trustees is three years or less as prescribed in the constitution or articles, and until their successors have qualified. Unless otherwise provided in the constitution or articles, immediately after their first election they shall be divided by lot into three classes, the first class retiring at the end of the first year, the second class at the end of the second year, and the third class at the end of the third year. After that, as near as may be, one-third of the whole number must be chosen annually. Two trustees may call a meeting of the board. When assembled, a majority of the whole number is a quorum for the transaction of business. Fifteen days before the expiration of the term of office of a trustee, the clerk shall give notice of the election of the trustee's successor, by posting it where the society statedly meets for worship. The notice must state the name of the trustee and the time and place of election. The minister or other officer of the church or society shall give public notice of the election to the congregation again at least one week before the election. These provisions apply to filling vacancies by death, resignation, or removal.