What happens to vapour pressure of solution if table sugar or table salt is added to water?

osmotic pressure is proportional to the molarity, C of the solution at a given temperature T. Thus:
Π = C R T 
Here Π is the osmotic pressure and R is the
gas constant.
Π = (n2 /V) R T 
Here V is volume of a solution in litres containing n2 moles of solute.
If w2 grams of solute, of molar mass, M2 is present in the solution, then n2 = w2 / M2 and we can write

$\mathrm{\pi V} = \frac{{\mathrm{w}}_2\mathrm{RT}}{{\mathrm{M}}_2}$


Thus, knowing the quantities w2, T, Π and V we can calculate the
molar mass of the solute.