The clerk of the city commission shall, at its next meeting, present the petition to the city commission, which shall proceed to reconsider the ordinance. If, within thirty (30) days after the filing of such petition, the ordinance be not repealed or amended as requested, the city commission shall provide for submitting the proposed repeal or amendment to a vote of the electors provided a majority of the committee named in the petition to represent the petitioners shall, by writing filed with the clerk of the city commission within twenty (20) days after the expiration of the said thirty (30) days, so require. In so doing the city commission shall be governed by the provisions of Section 50 hereof respecting the time of submission and the manner of voting on ordinances proposed to the city commission by petition; excepting that the question of calling a special election for such purpose shall be determined by the demand and number of signers of the petition requesting the repeal or amendment of such ordinance, which number shall be twenty-five percent (25%) of the registered voters in the municipality at the last regular municipal election; and excepting further that the city commission may call, and fix the time for, a special election for such purpose, if in its judgment the public interest will be prejudiced by delay.
   If, when submitted to a vote of the electors, such repeal or amendment be approved by a majority of those voting thereon, it shall thereupon go into effect as an ordinance of the city; but, if any such amendment is clearly separable from the remainder of the ordinance and does not materially affect the other provisions of such ordinance, all sections of the ordinance except that sought to be amended and those dependent thereon shall take effect as though no referendum of any portion of the ordinance had been demanded.