Question

On a certain day, the exchange rate was 60 U.S. dollars for 50 euro. How many U.S. dollars were 70 euro worth that day?

Answer 1

`\bf \begin{array}{ccll} \$ US&\$Euro\\ \cline{1-2} 60&50\\ x&70 \end{array}\implies \cfrac{60}{x}=\cfrac{50}{70}\implies \cfrac{60}{x}=\cfrac{5}{7}\implies \cfrac{60\cdot 7}{5}=x\implies 84=x`