OK so if they ring at 6AM together then they would ring like this from now on:
ANSWER: they ring together next at 9:20
Bell 1: 6:25 Bell 2: 6:40
Bell 1: 6:50 Bell 2: 7:20
Bell 1: 7:15 Bell 2: 8:00
Bell 1: 7:40 Bell 2: 8:40
Bell 1: 8:05 Bell 2: 9:20
Bell 1: 8:30 Bell 2: 10:00
Bell 1: 8:55 Bell 2: 10:40
Bell 1: 9:20 Bell 2: 11:20