The observed values are given in the table shown in the question. The line of best fit is given to be:

where x is the average monthly temperature and y is the heating cost.
A residual is a difference between the observed y-value (from scatter plot) and the predicted y-value (from regression equation line). The formula will be:

QUESTION A
The average monthly temperature is 24.9:

Observed cost:

Predicted cost:

Residual:

QUESTION B
The average monthly temperature is 35.9:

Observed cost:

Predicted cost:

Residual:
