At 6:00 a.m. the temperature at Fairbanks was -24 degrees and at Buffalo, it was -8 degrees.
To determine how much lower the temperature is you have to calculate the difference between the higher temperature and the lower temperature.
"-8" is greater than "-24" (Remember that when you order a negative number, the greater the absolute value of the number, the smaller will be the negative number)
So you have to calculate the difference between -8 and -24 degrees
The temperature was 16 degrees lower in Fairbanks than in Buffalo.