Given that:
[tex]P=0.2x^3-10[/tex]Substitute 15 for x in the equation of P to find the profit earned by selling 15 items.
[tex]\begin{gathered} P(15)=0.2(15)^3-10 \\ =665 \end{gathered}[/tex]Substitute 5 for x in the equation of P to find the profit earned by selling 5 items.
[tex]\begin{gathered} P(5)=0.2(5)^3-10 \\ =25-10 \\ =15 \end{gathered}[/tex]Profit more earned by seeling 15 items than 5 items
[tex]\begin{gathered} =P(15)-P(5) \\ =665-15 \\ =650 \end{gathered}[/tex]