When the vapor density defined as the mass of a certain volume of the substance divided by the mass of the same volume of hydrogen.
So Vapor density = molar mass of gas/molar gas of hydrogen
when we have the molar mass of the tetraoxosulphate (VI) = 98 & and we have the molar mass of Hydrogen = 2 so by substitution.
∴ Vapor density = 98 / 2 = 49
