What is the % of a milk that is prepared by mixing 30 g of water with 50 g of powdered milk?

Mass of solute (milk powder in this case): 50 g Total mass of solution: mass of milk powder + mass of water= 30g+50g=80g $$ \frac{weight}{weight}\%=\frac{weight\:of\:solute}{weight\:of\:solution}\times100 $$ $$ concentration\:of\:milk\:powder=\frac{50}{30+50}\times100=62.5\:\frac{w}{w}\% $$