Let's evaluate the function for:
[tex]P(x)=13.50[/tex][tex]\begin{gathered} 9+1.5x=13.5 \\ \text{Solving for x:} \\ \text{Subtract 9 from both sides:} \\ 9+1.5x-9=13.5-9 \\ 1.5x=4.5 \\ \text{Divide both sides by 1.5:} \\ \frac{1.5x}{1.5}=\frac{4.5}{1.5} \\ x=3 \end{gathered}[/tex]She get 3 toppings