A pack of cinnamon-scented pencils sells for $9.00. What is the sales tax rate if the total cost of the pencils is $9.63

well, the pencils are 9 bucks, but they're selling for 9.63, meaning the tax is 0.63 or 63 cents.

now, if we take 9 to be the 100%, what is 0.63 off of it in percentage?

[tex]\bf \begin{array}{ccll} amount&\%\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ 9&100\\ 0.63&t \end{array}\implies \cfrac{9}{0.63}=\cfrac{100}{t}\implies t=\cfrac{0.63\cdot 100}{9}[/tex]