The regulations imposed and the districts created by the Zoning and Property Chapters may be amended from time to time by the City Council but no such amendments shall be made without public hearing before the Council and after a report has been made upon the amendment by the Planning and Zoning Commission. At least seven (7) days’ notice of the time and place of such hearing shall be published in a newspaper having general circulation in the City. In case the Commission does not approve the change, or in the case of a protest filed with the Council against a change in district boundaries signed by the owners of twenty percent (20%) or more either of the area of the lots included in such proposed change or of those immediately adjacent thereto and within 200 feet of the boundaries thereof, such amendment shall not be passed except by the favorable vote of three-fourths (3/4) of all the members of the Council.