Taking the library as the origin, the bookstore coordinates are 200 and the cinema coordinates are -50.

Xiaoying's way: -50+90- 160=- 120.

So his position is

Distance from the bookstore: 200-(- 120) = 320-320 meters south of the bookstore.

Distance to the library: 0-(-120) =120-120 meters south of the library.

Distance to the cinema: -50-(- 120) = 70-70 meters south of the cinema.