what would be the vapor pressure of water in a solution wiith 23.7g NaCl dissolved in 500mL of water at 50degrees centigrade

First, it isn't centigrade any longer but celsius. Second, you must look up the vapor pressure of H2O at 50 C. You can get that on the web OR look in your text or notes. I think ALL beginning chemistry text have a table of vapor pressure versus temperature.

Convert 23.7g NaCl to moles. That will give you moles Na^+ and moles Cl^-. Then convert 500 mL water to moles. (I would look up the density of water at 50 C and use that to calculate the mass of the 500 mL.)
mole fraction Na^+ = moles Na^+/total moles.
mole fractin Cl^- = moles Cl^-/total moles.
mole fraction H2O = moles H2O/total moles.
PH2O @ 50C = XH2O*Ponormal