What is the mole fraction of solute in a 3.84 m aqueous solution?

Answer is: mole fraction of solute is 0,065.
molality(aqueous solution) = 3,84 mol/kg.
Molality is a measure of the concentration of a solute in a solution in terms of amount of substance in a specified amount of mass of the solvent. 
n(solute) = 3,84 mol.
m(solvent-water) = 1 kg = 1000 g.
n(water) = 1000 g ÷ 18 g/mol = 55,55 mol.
mole fraction = 3,84 mol ÷ 3,84 mol + 55,55 mol.
mole fraction = 0,065 = 6,5%.