In the event of a protest against such district change or amendment to the regulations of this ordinance duly signed and acknowledged by the owners of 20% or more either of the areas of the land included in such proposed change or by the owners of 20% or more of the land immediately adjacent extending 100 feet therefrom, or by the owners of 20% or more of the land directly opposite thereto extending 100 feet from the street frontage of such opposite land, such changes or amendments shall not become effective except by the favorable vote of three-fourths of the full Village Board of Trustees.