Answer:
After 2 hours: -6°C.
After 5 hours: -15°C.
After hours: -1.5°C
1 hour ago: 3°C.
3 hours ago: 9°C.
4.5 hours ago: 13.5°C.
To find these values, you simply need to multiply the hours elapsed by 3°C. Subtract from 0°C for future temperatures, and ADD to 0°C for the past.
Let's say you are solving for the temperature in 5 hours. All you need to do is:
3°C× 5= 15°C. 0°C-15°C= -15°C
For the temperature 3 hours AGO, what you will need to do instead is:
3°C×3= 9°C. 0°C+ 9°C= 9°C.