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?

The temperature at 9 AM is (-13 f)

-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.