In 9 grams of ruby's there are 0.0198416 lbs, to achieve this take 9 and just divide by 453.5924.
How many lbs of emeralds are there in 6.8 grams? Just divide by 453.5924 to get the answer of 0.01499143 lbs.
You have 8.9 grams of gold but you need to know how many lbs that is. To get the answer divide by 453.5924 which gives you 0.01962114 lbs.
You've got 4.7 grams of silver but someone only wants to buy that in units of lbs, to change the units divide by 453.5924. Now you have 0.01036173 lbs.
To convert 6.9 grams into lbs divide by 453.5924 giving 0.0152119 lbs.