Final answer:
The regression line predicts that the gas used will be about 964 cubic feet per day when the temperature is 20F.
Step-by-step explanation:
The regression line, yhat = 1344 - 19x, predicts the amount of natural gas consumed (y) based on the outside temperature (x). To find the predicted gas consumption when the temperature is 20F, substitute x = 20 into the regression equation:
yhat = 1344 - 19(20)
yhat = 1344 - 380
yhat = 964 cubic feet per day
Therefore, when the temperature is 20F, the regression line predicts that the gas used will be about 964 cubic feet per day.