What is the best way to get to the Great Wall at Badaling from beijing Penta Hotel and how much?

Walk from the hotel to Chongwenmen MTR Station to take local subway line 2 to Jishuitan Station. Get out from Exit B and you can easily walk to Deshengmen to take bus no. 919 or 880, either of which can take you to Badaling directly.
MTR fare is CNY2 per person and the bus fare is CNY12 per person.

Thank you, Juno. How long does this take? If it is too long, is there a better way that is not too expensive?

Hi, the whole journey takes nearly two hours. Besides, you can also take the same MTR line to Xizhimen Station, and then walk from the exit A1 to BJ North Railway Station, where there are direct trains to Badaling, taking 1h and 15min.