The temperature in London was -12C. For the next 5 hours, it dropped 4 degrees Celsius every hour. Between 11 pm and midnight, the temperature dropped another 7 degrees celsius. What was the temperature at midnight?
So for 5 hours it dropped 20° C
then another 7°
final temp = -12 - 20 - 7 = -39° C
If this is London , UK, I don't think the temp ever was that low. Never!