Answer: -11 degrees Celsius
Explanation:
4:00 am = -16 degrees
You know that 4:00am is four hours after midnight and you know that the temperature decreases by 1.75 degrees every hour so during that time it has dropped by:
1.75x4=7 degrees
Because it is -16 at 4:00am, you know it was 7 degrees higher at midnight
-16+7=-11
It was -11 degrees at midnight