Xiaole and her mother went to the library. When she left, Xiaole looked at the clock on the wall. At 9: 30, when I got home in the afternoon, Xiaole looked at the clock in the mirror and pointed to 7 o'clock sharp. How long did Xiaole and her mother stay in the library? \x0c

Residence time = 12-9.5+7=9.5 hours =9 hours and 30 minutes.