Asolution has 23.22% mass/concentration of a particular solvent what is the mass of solute dissolved in 2.5 liter of solvent?

The answer for #3 is c but i don't know why

0.09 moles of sodium sulfate in 12 ml of solution

If a molecule with a molecular formula of c13h18 is treated with an excess of h2 in the presence of finally divided pt metal under conditions required for maximum hydrogenation of the molecule to give a molecule with a formula c13h24, how many rings are in the molecule?