After one week, Greg's watch has lost 3.5 minutes. If the watch continues to lose time at the same rate, we can say that the change in time is 3.5 minutes per week. Based on this rate, we can find the overall change in time after 8 weeks.
(3.5 minutes/week) x (8 weeks) = 28 minutes
The overall change in time after 8 weeks will be 28 minutes.