How to calculate the mass fraction of sugar in 50 g of water, the mass of sugar is 5.5 g?

The mass fraction w is the ratio of the mass of the solute m (r.v.) to the mass of the solution m (r-ra), which is the sum of the mass of the solvent m (r-la) and the mass of the solute. Expressed in fractions or percentages (the result in fractions is multiplied by 100%)

w = m (r.v.) / m (r.v.) = m (r.v.) / (m (r.v.) + m (r.v.)) = 5.5 / (50 + 5.5) = 0.099 or 9.9%