Final answer:
To create a residual plot, calculate the residuals by subtracting the predicted value from the actual value, and then plot the residuals against the x-values.
Step-by-step explanation:
To create a residual plot, we need to calculate the residuals for each data point, which can be found by subtracting the predicted value (ŷ) from the actual value (y). In this case, the predicted value can be found using the equation of the least-squares regression line: ŷ = 68.5 + 11.4x. Once the residuals are calculated, they can be plotted on the y-axis against the x-values (number of years the school has been open) on the x-axis. This will give us a plot that shows how the actual values deviate from the predicted values.