What is the ticket fare for bus from Xuan Wu Gate to Longqing Gorge

There is no direct buses for Longqing Gorge directly. You can take the subway line 2 to reach Jishuitan Station and then take a taxi to reach Deshengqiao West Station to take bus 919 to reach Yanqing Railway Station. Then you can take a local taxi to reach Yanqing NorthRailway Station to take bus 875 to reach the Longqing Gorge directly.
The bus ticket fare is around 12RMB from BJ to Yanqing. For 875 bus, the fare is about 6 RMB.