First of all, analyze the topic: two people leave the library and go home at the same time, and arrive home at the same time after 0.3 hours, which shows that the distance from home to the library is the same. So find out the distance from the library to Mr. Li's house, that is, find out the distance from Xiao Qiang's house to the library.

Distance = speed × time

15× 0.3 = 4.5km.

The distance of Xiao Qiang Library is 4.5 kilometers.