Regarding the church council, ¶ 252.6 in the 2016 Book of Discipline states, "The members present and voting at any duly announced meeting shall constitute a quorum."
There is an exception for the board of trustees, "A majority of the members of the board of trustees shall constitute a quorum."(¶ 2532)
For other committees not specifically mentioned in the Discipline, a quorum would depend on local church policies and procedures.