Which subway line should i take from sun World Hotel Wang fu jing to Beijing Silk Street Market?

You may refer to the Sunworld Dynasty Hotel Wang fu jing, right?
You’d first walk to the east to Deng Shi Kou Station, take subway line 5 and get off at Dong Dan. Then transfer to line 1 to Yong An Li Station. Get out from exit A and u can easily walk to the market.

and what exit to take from silk market to dengshikou back to hotel? when we buy subway tickets, do we just tell them where we are going? I understand that it varies depending on how far we are going.

Walk from Silk Street to Jianguomen Station to take the subway line 1 to Dongdan Station, where you can transfer to Line 5 to Dengshikou Station. Then take the Exit A and then walk westwards along the Baishu Hutong alley for 500 yards, you will reach the hotel.

Inside the subway station, there are automatic ticketing machine, just choose the destination, Dengshikou Station on line 5. Then the fare and the route will be showed. Remember to prepare some changes.