Answer : The mass of sodium bromide added should be, 18.3 grams.
Explanation :
Molality : It is defined as the number of moles of solute present in kilograms of solvent.
Formula used :

Solute is, NaBr and solvent is, water.
Given:
Molality of NaBr = 0.565 mol/kg
Molar mass of NaBr = 103 g/mole
Mass of water = 315 g
Now put all the given values in the above formula, we get:


Thus, the mass of sodium bromide added should be, 18.3 grams.
Answer/ explanation :
The find the mass,
We use this formula
Number of mole = mass/ molar mass
Since number of mole = 3.25mol
Number of mass be x
Molar mass of H2SO4
H - 1.00784 * 2= 2.01568
S - 32.065
O - 15.999 * 4 = 63.996
Note there are 2 moles of H and 4 moles of O and 1 mole of S
Molar mass of H2SO4 = 2.01568 + 32.065 + 63.996
= 98.07668g/mol
Number of mole= 3.25mol
3.25 = x / 98.07668
x = 3.25 * 98.07668
= 318.749g
Therefore, the number of mass is 318.749g