Let the % of the sames tax be x, then
[tex]400\left( \frac{100+x}{100} \right)=432 \\ \\ \Rightarrow\left( \frac{100+x}{100} \right)= \frac{432}{400} =1.08 \\ \\ \Rightarrow100+x=100(1.08)=108 \\ \\ \Rightarrow x=108-100=8\%[/tex]
Therefore, the percent of the sales tax is 8%.
