Answer: 700.067 g
Step-by-step explanation:
Given : The pharmacist uses 67mg, 100g and 0.6 kg of drug to compound 3 separate prescription.
We know that 1 gram= 1000 milligram
and 1 kilogram = 1000 grams
Then, By UNITARY METHOD, 
Now, We convert each amount of drug into grams as ,

AND

Now, the total drug used by Pharmacist (in grams) = 
Hence, Pharmacist used 700.067 g of total drug.