The board of trustees shall hold a meeting at least once each three months, and shall designate the time and place thereof. Three trustees shall constitute a quorum at any meeting of the board. Each trustee shall be entitled to one vote on each question before the board and at least three concurring votes shall be required for a decision by the board at any of its meetings. The board shall adopt its own rules of procedure and shall keep a record of its proceedings. All meetings of the board shall be public.