Question 1015437
Here are the 3 choices -

Drawer 1  G-G

Drawer 2  S-S

Drawer 3  G-S

You chose S, so there is a 1 in 3 chance the other coin is G. 
Because, you could have S(1) or S(2) or S(3) in your hand, so, respectively, the other coin choices are S(2), S(1), or G(3)

Once you draw a coin, and see it is silver, you know you've chosen from Drawer 2 or 3. But as I stated, there are now still 3 possibilities, (1) you've chosen the silver coin from drawer 3, (2) you've chosen the first silver coin from drawer 2 or (3) the second silver coin from drawer 2. Only one of these three silver coins sits with the gold coin.