A benzene-toluene mixture containing 50% benzene by mole fraction is subjected to differential distillation at atmospheric pressure. The liquid remaining after the distillation of a portion of the initial solution contains 20% benzene by mole fraction. Find the average composition of the distilled portion.

The pure component vapor pressures of the benzene-toluene system that obey Raoult's law

T, C	Pbenzene ,mmHg	Ptoluene ,mmHg
80.1	760	-
85	877	345
90	1016	405
95	1168	475
100	1344	557
105	1532	645
110	1742	743
110.6	1800	760