Question

There is a sales tax of $21 on an item that cost $217 before tax. A second item.cost $93 before tax. What is the sales tax on the second itme?

Answer 1

if 217 is the 100%, how much percentage is 21?

well   $\bf \begin{array}{ccllll} amount&\%\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ 217&100\\ 21&x \end{array}\implies \cfrac{217}{21}=\cfrac{100}{x}\implies x=\cfrac{21\cdot 100}{217} \\\\\\ x\approx 9.6774\%$

now, the $93 item, let's say 93 is the 100%, then

$\bf \begin{array}{ccllll} amount&\%\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ 93&100\\ x&9.6774 \end{array}\implies \cfrac{93}{x}=\cfrac{100}{9.6774}$

solve for "x".