How much from the capital airport to the great wall for two people? And how long is It gonna take?

Do you refer to Badaling Great Wall?
If yes, the fare is CNY 300 by taking a taxi from the airport. It will take around 1.5 hours on the way.
Or you can take airport shuttle bus line 4 and get off at Gongzhufen Station. It will take around 50 mins on the way. And the ticket fare is CNY 24 per adult.
Then transfer to public bus no.919 at South Madianqiao Station, and get off at Ancient Badaling Great Wall Station. After arriving, walk to the scenic area directly. It will take around 2 hours on the way.