The idea here is that the vapor pressures of benzene and toluene will contribute to the total vapor pressure of the solution proportionally to their respective mole fraction - this is known as Raoult's Law.
Mathematically, you can express this by the following equation
$P_"sol" = chi_"benzene" * P_"benzene"^@ + chi_"toluene" * P_"toluene"^@$ , where
Now, mole fraction is defined as the ratio between the number of moles of a component of a solution and the total number of moles present in the solution.
Since you only have two components to this solution, benzene and toluene, you can say that
$chi_"benzene" + chi_"toluene" = 1$
Let's say that the mole fraction of benzene is
$x = 1 -y$
and
$P_"total" = x * P_"benzne"^@ + (1-x) * P_"toluene"^@$
$40. color(red)(cancel(color(black)("torr"))) = x * 75color(red)(cancel(color(black)("torr"))) + (1-x) * 22color(red)(cancel(color(black)("torr")))$
$40. = 75x + 22 - 22x$
$40 - 22 = 53x implies x = 18/53 = 0.3396$
This means that you have
y = 1 - 0.3396 = 0.6604$
The mole fractions of benzene and toluene in the solution will thus be - rounded to two
$chi_"benzene" = color(green)(0.34)" "$ and$" "chi_"toluene" = color(green)(0.66)$