Question: Sandy wants to lose as much weight as Joey does but needs 4 weeks to lose the same amount of weight that Joey loses in a single week. If Joey loses 8 pounds in 4 weeks, how many weeks will it take Sandy to lose the same amount of weight?
Answer: 
Joey loses 8 pounds / 4 weeks = 2 pounds per week.
In order to match Joey, Sandy should lose 2 pounds / 4 = 0.5 of a pound per week.
To find the number of weeks it will take, divide the number of pounds by the rate of weight loss: 8 pounds / 0.5 pounds/week = 16 weeks