Answer:
2 mL
Explanation:
If the drug is mixed in a solution of 0.5%, it means that for each ml of the solution, there is 0.5% or 0.005 grams of the drug. In order to get 10 mg of the drug, the volume required is:

You should add 2 mL of the solution.
*Note that the volume of the bag should not be used since the amount of drug needed was specified in weight and not in concentration.