so, if we take 1.20 to be the 100%, what is 0.80 off of it anyway?
[tex]\bf \begin{array}{ccll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
1.20&100\\
0.80&p
\end{array}\implies \cfrac{1.20}{0.80}=\cfrac{100}{p}\implies p=\cfrac{0.80\cdot 100}{1.20}[/tex]
