Answer: She (Serena) made 30 grams of 33.33% sugar syrup. Solution: 10 grams sugar + 20 grams water As 10 grams of sugar added to 20 grams of water, total mixture became 30 grams. Percentage of sugar in total mixture (sugar syrup) = 10 grams sugar in 30 grams syrup. % by mass = [(mass of solute) / (mass of solute + mass of solvent)] * 100 This gives = [(10) / (10+20)] * 100 = 33.33%