She bought the painting at a low price and resold it for a good profit a week later.

resold 是动词 resell 的过去式，resell 由前缀 re-（表示“再次”）和动词 sell（卖）组成，意思是“转卖、再次出售”。resold 表示"转卖"这个动作已经完成。