[tex]\bf \begin{array}{ccll} hours&pages\\ \cline{1-2} 12&360\\ x&400 \end{array}\implies \cfrac{12}{x}=\cfrac{360}{400}\implies \cfrac{12}{x}=\cfrac{9}{10} \\\\\\ 120=9x\implies \cfrac{120}{9}=x\implies \cfrac{40}{3}=x\implies 13.\overline{3}=x[/tex]
