Amendments are changes in motions. There are two kinds of amendments. Primary amendments must be germane to the motion they amend, and may be amended themselves. Secondary amendments apply to primary amendments and must be germane to the primary amendment. Secomdary amendments cannot be amended.
Amendments can entirely replace a motion with another motion related to the same subject.
Amendments still must be seconded. Voting A quorum is required for any action of the council to be binding. No one is required to vote. Therefore, a majority is more than half the votes cast. It is not half of those members present.