Hi newcomer and welcome to the Tom's hardware forum.
1- What mobo do u have? Check the mobo specifications for know that.
2- Both 3200 and 2700 are DDR so if u are using 3200 I think that u can install 2700 without problems.
3- Keep in mind that if u install both 3200 and 2700 the mobo only can run at the lower speed that in this case is 2700
From the Pic that was posted earlier by saint19 it looks like that would be the correct method -- It shows 2 orange and 2 blue slots and normally the Maker will color code them so that you know which 2 sockets are linked for dual channel !