Hello!
To solve exercise 9, we must use the rule of three.
Note that the initial price was R12 (corresponds to 100%).
The new price is R10.8 (we'll consider x%).
Using the rule of three, we will have:
[tex]\begin{gathered} \frac{12\rightarrow100\%}{10.8\rightarrow x\%} \\ \\ 12\cdot x=10.8\cdot100 \\ 12x=1080 \\ x=\frac{1080}{12} \\ \\ x=90\% \end{gathered}[/tex]
Now, let's calculate the difference between the initial percentage and the new percentage:
[tex]100\%-90\%=10\%\text{ of decrease}[/tex]
Answer:
10% of decrease.
