12 geese left per hour. At 7:30 am there were 18 less geese than there were at 6:00 am. Since there was 1.5 hours between each time, and we know that 2/3 of 1.5 hours is 1 hour, we can solve using this equation:
2/3 * 18 = 12.
6.7m questions
8.8m answers