Should the council decide to submit the proposal to the electors, it shall be submitted at the next election held in the city for any other purpose, or, in the discretion of the council, at a special election called for that specific purpose. In the case of an initiatory petition, if no election is to be held in the city for any other purpose within one hundred and fifty days from the time the petition is presented to the council and the council does not adopt the ordinance, then the council shall call a special election within sixty days from such time for the submission of the initiatory proposal. The result shall be determined by a majority vote of the electors voting thereon, except in cases where otherwise required by law.