The Council may, by the affirmative vote of at least two-thirds of its members, submit any proposed amendment to the Charter to the elector; or, upon receipt of a petition signed by not less than 15% of the electors of the City voting at the last preceding general election setting forth any proposed amendment to the Charter, it shall submit such proposed amendment to the electors. The Council shall determine the manner of the submission of any proposed amendment to the electors to the extent that such submission is not governed by the Constitution of Ohio. If any such proposed amendment shall be approved by a majority of the electors voting thereon, it shall become a part of this Charter and become effective as provided in such amendment except that, if two or more inconsistent proposed amendments on the same subject shall be submitted at the same election, only the one of such amendments receiving the largest affirmative vote, not less than a majority, shall become a part of the Charter.