Within thirty (30) days after the enactment by Council, of any ordinance or resolution which is subject to a referendum under the laws of the State of Ohio, a petition signed by qualified electors equal in number to no less than ten percent (10%) of the total votes cast at the last regular municipal election, may be filed with the Council requesting the ordinance or resolution be repealed, or submitted to a vote of the electors. When said petition is filed the Clerk shall first ascertain the sufficiency of the petition, and if found sufficient, the Council shall thereupon, within thirty (30) days of the filing of such petition reconsider such ordinance or resolution. If Council fails to repeal said ordinance or resolution within thirty (30) days the Council shall submit it to a vote of the electors at the next general or municipal election occurring more than ninety (90) days after the filing of such petition; but if, such petition is signed by qualified electors equal in number to at least twenty percent (20%) of the total votes cast at the last regular municipal election, the date of the election may be fixed therein, which may be a special election to be held at any time more than ninety (90) days after the filing of such petition.