Answer:
Since the workers repair an equal distance each week until the repair is completed, we can divide the remaining distance by the number of weeks left (7 weeks) to find out how many miles of highway they repair in each of those 7 weeks.
21 miles ÷ 7 weeks = 3 miles per week
Therefore, the workers repair 3 miles of highway each week for the following 7 weeks until the repair is completed.