Let's take the price in August as the 100%, then we can find the difference between the two months with a rule of three:
[tex]\begin{gathered} 4.26\rightarrow100\text{ \%} \\ 3.92\rightarrow x\text{ \%} \\ \Rightarrow x=\frac{3.92(100)}{4.26}=\frac{392}{4.26}=92 \\ x=92\text{ \%} \end{gathered}[/tex]Now, we substract 100% from the total to get the following:
[tex]92-100=-8\text{ \%}[/tex]therefore, there was a decrease of 8% in the price of gas from August to September
