We simply multiply the mole fraction of water times the vapor pressure of water in the initial system and that is 5.51 divided by the total number of moles. The mole fraction 5.56
plus 1.85 gives us some fraction. That fraction is multiplied by 500 and that gives us 375.17
mmhg and that's the bigger pressure of these water molecules. Now it should be less. And that's because we have less water molecules on the surface, because now we have ethylene glycol molecules on the surface. And so less water molecules are evaporating.