A dealer records the age x of six cars in months and the value y of each in hundreds of pounds: x =…

Step 1. The line. $b = \dfrac{-1245}{1750} = -0.711$. The intercept is $67.5 + 0.711 \times 35 = 92.4$. So $\hat{y} = 92.4 - 0.711x$.

Step 2. Inside the data. At $x = 35$: $92.4 - 24.9 = 67.5$ hundred pounds, which is the mean value, because $35$ is the mean age.

Step 3. Outside the data. At $x = 100$: $92.4 - 71.14 = 21.26$ hundred pounds. This is extrapolation.

Step 4. The fit. $r^2 = 0.996$, so the line explains $99.6\%$ of the variation in value.