let's say is "x", thus "x" is the 100%, so, if "x" is the 100% and we know 12 is 20% of that, what's "x"?
[tex]\bf \begin{array}{ccll} amount&\%\\ \cline{1-2} x&100\\ 12&20 \end{array}\implies \cfrac{x}{12}=\cfrac{100}{20}\implies \cfrac{x}{12}=5\implies x = 60[/tex]
