Question

A merchant sold an item at a profit of $12. If this amount was

40% of what he paid for it, how much did the item cost him?
number is

Answer 1

well, the item really cost him "x", which oddly enough is the 100%, and we know that 12 is 40% of that, so

`\begin{array}{ccll} Amount&\%\\ \cline{1-2} x & 100\\ 12& 40 \end{array} \implies \cfrac{x}{12}~~=~~\cfrac{100}{40} \\\\\\ \cfrac{x}{12} ~~=~~ \cfrac{5}{2}\implies 2x=60\implies x=\cfrac{60}{2}\implies x=30`