well, if we take 40 to be the 100%, what is 14 off of it in percentage?
[tex]\begin{array}{ccll} amount&\%\\ \cline{1-2} 40 & 100\\ 14& x \end{array} \implies \cfrac{40}{14}~~=~~\cfrac{100}{x}\implies \cfrac{20}{7}=\cfrac{100}{x} \\\\\\ 20x=700\implies x=\cfrac{700}{20}\implies x=35[/tex]
