Given:
m = -8 degrees/hour, the rate of change of temperature
Let x = hours
Let y = temperature, °F
Then y = -8x + b
where b = constant
When x = 0, then y = b.
Therefore b = initial temperature
If the temperature drops by at least 36 °F in the next x hours, then
b - y(6) ≥ 36
b - (-8x + b) ≥ 36
8x ≥ 36
x ≥ 4.5 hours
Answer: At least 4.5 hours
