A. To estimate the temperature I would follow the trend of a -2.8 drop plus .6. So the estimated new temperature would be 5.6-2.8= 2.8-2.2= .6- 1.6= -1
B. To calculate it, you would do the same math as above as I believe my answer is correct.
C. Peter can use the estimate to determine his answer is wrong because it follows the opposite of the trend in where the temperature goes. The trend is negative and decreasing, therefore, numbers higher than 5.6 would not be possible anywhere in the graph