The vapor pressure at 28 Co is of 28.3 mm Hg. Based on the Dalton’s law regarding partial pressure of gas mixture the total pressure is defined as follows: P = p(Ne) + p(He) + p(H2O), thus, partial pressure of Neon equals: p(Neon) = P - p(He) - p(H2O) = 745 mm Hg – 368 mm Hg – 28.3 mm Hg = 348.7 mm Hg