If I understood your question correctly the answer will be:
Weigh 97 grams of Cerium dioxide and 3 grams of Copper dioxide and mix them with your vehicle up to 100 mL. This makes the concentrations of Cerium dioxide 97%w/v and Copper dioxide 3%w/v.
Weigh 97 grams of Cerium dioxide and 3 grams of Copper dioxide and mix them with your vehicle up to 100 mL. This makes the concentrations of Cerium dioxide 97%w/v and Copper dioxide 3%w/v.