Question

elapsed time is 3 hours & 56 minutes. End time is 1:40 p.m. What is the start time?

Answer 1

3 hours and 56 minutes before 1:40 pm is 9:44 am

Answer 2

1:40 - 1 hour is 12:40. (2 hours and 56 min left)
12:40 - 40 min is 12:00 (2 hours and 16 min left)
12:00 - 2 hours is 10:00 (16 min left)
10:00 - 10 min is 9:50 (6 min left)
9:50 - 6 min is 9:44.

The start time is 9:44 A.M