At 3am the temperature is -5 f . between 3 am and 6am, the temperature drops by 12 f. between 6 am and 9 am , the temperature rises by 4 f. what is the temperature at 9 am?

-5 - 12
When subtracting integers, add by the opposite sign.
-5 + (-12) = -17

-17 + 4
When adding opposite signs, you subtract the greater number from the smaller number. Keep the sign that the larger number has.
-17 - 4 = -13.

The temperature is -13F at 9 AM.