Combination: Three-foot residence: Discussing Beijing, Baotou, Tianjin, the requirement is to find out their residence and occupation based on the following conditions: (1) Although Bai Ying's all relatives and close friends are in Beijing, he only occasionally visits the capital; (2) Among these three people, two of their occupations and the first letter of the city they live in are the same as the first letter of their names; (3) The tractor driver's wife is Bai Ying's sister.
From (1)(3) $\Rightarrow$ Bai Ying is not a tractor driver and does not live in Beijing. And “the tractor driver must live in Beijing”. Assuming Tang Li is the tractor driver and lives in Beijing, from (2) $\Rightarrow$ Bai Min and Bao Min must have the first letter of their residence and occupation in Chinese pinyin be “$B$”, which is impossible (Baotou “$B$”, Tianjin “$T$”). Therefore, it can only be “Bao Min is the tractor driver and lives in Beijing” $\Rightarrow$ “Tang Li is the postman and lives in Tianjin”, “Bai Ying is the broadcaster and lives in Baotou.”