Ten hours. Subtract the smaller number from the larger. Then subtract the remainder from 12.
73 hours.
from 7:30 am till 7:00 pm it is 11 hours and a half.
There are 7 hours from 3 pm to 10 pm.
7 and a half hours
13 + 24k hours where k is an integer.
7 hours and 30 minutes
19
There are 17 hours between 2 am and 7 pm.
12
It is seven hours from 9 AM to 4 PM.
8 hours.
7 pm to 7 am is 12 hours 7 am to 8 am is 1 hours → 7 pm to 8 am is 12 + 1 = 13 hours.