Question

I have 20 cookies requires 1/3 cup of butter to make how many cups of butter do I need to make 12 cookies

Answer 1

`\bf \begin{array}{ccll} cookies&\stackrel{butter}{cups}\\ \cline{1-2} 20&(1)/(3)\\\\ 12&x \end{array}\implies \cfrac{20}{12}=\cfrac{~~(1)/(3)~~}{x}\implies \cfrac{5}{3}=\cfrac{~~(1)/(3)~~}{(x)/(1)}\implies \cfrac{5}{3}=\cfrac{1}{3}\cdot \cfrac{1}{x} \\\\\\ \cfrac{5}{3}=\cfrac{1}{3x}\implies 15x=3\implies x = \cfrac{3}{15}\implies x = \cfrac{1}{5}`