A large box P containing 15 cans of biscuits weighs 23 kg and weighs 500g when empty. A box containing 8 cans of the same biscuits Q weighs 12.3kg. Box Q What is the mass when the box is empty?

300 g or 0.3 kg

Step-by-step explanation:

23 kg - 500g = 22.5 kg

each can of biscuits weighs 22.5 : 15 = 1.5 kg

if the box Q weighs 12.3kg when there's 8 box of biscuits then

8 * 1.5 = 12 kg is the weight of biscuits and the remaining 300 g is box Q's weight