I'll help you navigate from Xizhimen to the west gate of Peking University. You can refer to it

Bus route: Daxing Line of Metro Line 4 → 7 18, the whole journey is about 9.9 kilometers.

1. Take Daxing Line of Metro Line 4 from Xizhimen and arrive at Zhongguancun Station after 6 stops.

2. Walk about 160m to Zhongguancun South Station.

3. Take bus No.718, and arrive at Ximen Station of Peking University after three stops (you can also take bus No.332, express 106 and bus No.608).