if we take 1200 to be the 100%, then what is 210 off of it in percentage?
[tex]\bf \begin{array}{ccll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
1200&100\\
210&x
\end{array}\implies \cfrac{1200}{210}=\cfrac{100}{x}\implies x=\cfrac{210\cdot 100}{1200}[/tex]
