At 7:00 a.m. yesterday, Sherry correctly determined what time it had been 100 hours before. What was her answer? (Be sure to include "a.m." or "p.m." in your answer.)
Since $100=4 \cdot 24+4$, then 100 hours is 4 days and 4 hours.

The time 4 days before 7:00 a.m. is also 7:00 a.m.

The time 4 hours earlier than this is 3:00 a.m.

Thus, the time 100 hours before 7:00 a.m. is 3:00 a.m.

ANSWER: 3:00 a.m.