the original cost is "x", which is the 100% of the original price, and we also know that €336 is its price increased by 40%, namely 100% + 40% = 140%, so
[tex]\begin{array}{ccll} amount&\%\\ \cline{1-2} x & 100\\ 336& 140 \end{array} \implies \cfrac{x}{336}~~=~~\cfrac{100}{140} \\\\\\ \cfrac{x}{336}=\cfrac{5}{7}\implies 7x=1680\implies x=\cfrac{1680}{7}\implies x=240[/tex]
