Where $x_{A}$ and $x_{B}$ are mole fraction of $A$ and $B$ in liquid phase.

$P_{A}^{0}$ and $P_{B}^{0}$ are vapour pressures of pure liquids.

Moles of $C H C l_{3}=\frac{25.5}{119.5}=0.213$

Moles of $C H_{2} C l_{2}=\frac{40}{85}=0.471$

Mole fraction $X_{C H C l_{3}}=\frac{0.213}{0.471+0.213}=\frac{0.213}{0.684}=0.311$

$X_{C H_{2} C l_{2}}=\frac{0.471}{0.684}=0.689$

vapour pressure $=0.311 \times P_{C H C l_{3}}+0.689 P_{C H_{2} C l_{2}}$

$=0.311 \times 200+0.689 \times 41.5=90.7935 \;\mathrm{mm} \mathrm{Hg}$