So let's see here...
6:00 A.M. temperature is 33°F.
12:00 P.M temperature increased by 10°F making it 43°F.
3:00 P.M. temperature increased by another 12°F making it 55°F.
At 10:00 P.M it would decrease by 15°F making it 40°F.
The temperature would need to fall (or decrease) by 7°F to reach the original temperature of 33°F
Hope this helped!