Answer:
The weather changed by 5°F in 12 hours
Step-by-step explanation:
It was 15°F at 6 A.M. which means it was morning. Then the time changes to 6 P.M. which means it is now the afternoon. In the time that has passed the temperature increased to 20°F.
(I'm not sure if this was the answer you were looking for but I hope this helped)
