How do I find mass using Molality

How many grams of sucrose, C12H22O11, must be added to 80.0 g of water to prepare a 0.250
molal solution

moles sucrose / 0.08 kg water = 0.250 mol solute/kg solvent
so moles sucrose = 0.250 mol/kg * 0.080 kg = 0.020 mol.

mass sucrose = mol * molar mass = 0.02 mol * 342.3 g/mol = 6.85 g.

0.25 molal is 0.25 mole per kg solvent. You have 0.080 kg solvent so you need 0.02 moles of sucrose. Calculate the molecular weight of sucrose and multiply by 0.02 moles.