Temperature of thing = 25°C
Rate of decreasing of temperature = -3°C per minute
Total decrease in temperature of thing after decreasing
from 25°C to – 2°C = (- 2) – 25
= -2 – 25
= – 27°C
Time taken to reach upto – 27°C at the rate of 3°C per minute = 27°C x 1/3°C per minute
= 9 minutes.