In case of a protest against such amendment, change, modification, or repeal, signed by the owners of 20% or more, either of the area or in the lots included in such proposed changes or of those immediately adjacent in the rear thereof extending 100 feet therefrom, or of those directly opposite thereto, extending 100 feet from the street frontage of such opposite lots, such amendment, supplement, change or modification, shall not become effective except by the favorable vote of the 2/3 of all the members of the Borough Council authorized to vote thereon.