To find the temperature at 9.00 am, we have:
At 3:00 am the temperature is -5 °F = -5 °F
Between 3 a.m and 6a.m, the temperature drops by 12 °F = -5 - 12 = -17 °F
Temperature drops by 12°F means -12°F
Between 6 a.m. and 9 a.m, the temperature rises by 4 °F = -17 + 4 = -13 °F
Temperature rises by 4 means +4°F
Therefore the temperature at 9:00 am is -13 °F
ANSWER:
-13 °F