Solution with negative deviation has

$ \mathrm{P}_{\mathrm{T}}<\mathrm{P}_{\mathrm{A}^0} \mathrm{X}_{\mathrm{A}} +\mathrm{P}_{\mathrm{B}^0} \mathrm{X}_{\mathrm{B}} $

$ \mathrm{P}_{\mathrm{A}}<\mathrm{P}_{\mathrm{A}^0} \mathrm{X}_{\mathrm{A}} $

$ \mathrm{P}_{\mathrm{B}}<\mathrm{P}_{\mathrm{B}^0} \mathrm{X}_{\mathrm{B}} $

If vapour pressure decreases so boiling point increases.