The board shall fix a reasonable time for the hearing of an application or appeal, give public notice thereof as well as due notice to the parties in interest and make its decision within ninety days of the filing of the application or appeal. In exercising its powers the board may reverse or affirm, wholly or partly, or may modify, an order, requirement, decision or determination appealed from. The concurring vote of a majority of the membership of the board shall be necessary to reverse any order, requirement, decision or determination of an administrative officer or to decide in favor of the applicant on any matter upon which it is required to pass under the ordinance or to effect any variance from the ordinance. The board shall keep minutes of its proceedings and other official actions which shall be filed in the office of the board and shall be public records. The chairman of the board, or in his absence the acting chairman, may administer oaths and compel the attendance of witnesses.