$($a$)$

Show the material balance of the tower as in Figure $(1).$ i can't understand why xw is $100/18$

$x_b=\frac{\frac{96}{100}(y_b)}{x_w+\frac{96}{100}(y_b)}$

$x_b=\frac{\frac{95}{100}(0\mathrm{.}07)}{\frac{100}{18}+\frac{95}{100}(0\mathrm{.}07)}$ question : polluted air : $MW=40,0\mathrm{.}07$mol$\%,1$atm, $90F,15000$acfm, $it$ must $be$ removed $96\%,absorberis$ pure water.