Final answer:
To predict the median income of a region where 30% of adults 25 years and older have at least a bachelor's degree, use the least-squares regression equation.
Step-by-step explanation:
To predict the median income of a region where 30% of adults 25 years and older have at least a bachelor's degree, you can use the least-squares regression equation. In this equation, the x-value represents the percentage of adults with a bachelor's degree.
Substitute the x-value of 30 into the equation: y = 659.8(30) + 15,673.
Calculating this equation will give you the predicted median income for the region.