What is the true solution to \( 2 \ln e^{\ln 5 x}=2 \ln 15 \) ? \( \begin{array}{l}x=0 \\ x=3 \\ x=9 \\ x=15\end{array} \) \( \begin{array}{l}x=\end{array} \) \( \begin{array}{l}x=\end{array} \)

Find the quotient and simplify the result. \( \frac{10 x^{4}}{y^{2}}+\frac{5 x^{4} y^{2}}{8} \) \( \frac{10 x^{4}}{y^{2}}+\frac{5 x^{4} y^{2}}{8}=\square \) (Simplify your answer.)

Subtract the rational expressions. \( \frac{5 x-7}{x^{2}-8 x+15}-\frac{4 x-4}{x^{2}-8 x+15} \) \( \frac{5 x-7}{x^{2}-8 x+15}-\frac{4 x-4}{x^{2}-8 x+15}=\square \) (Simplify your answer.)

Find the product and simplify if possible. \[ \frac{5 x}{y^{2}} \cdot \frac{4 y}{7 x} \] \( \frac{5 x}{y^{2}} \cdot \frac{4 y}{7 x}=\square \) (Simplify your answer. Use integers or fractions for any numbers in the expressio exponents only)

Find the quotient and simplify the result. \[ \frac{x+3}{9-x}+\frac{x^{2}-11 x+30}{x^{2}-15 x+54} \] \( \frac{x+3}{9-x}+\frac{x^{2}-11 x+30}{x^{2}-15 x+54}=\square \) (Simplify your answer.)

Let \( y \) represent the total cost of publishing a book (in dollars). Let \( x \) represent the number of copies of the book printed. Suppose that \( x \) and \( y \) are related by the equation \( y=1100+10 x \). Answer the questions below. Note that a change can be an increase or a decrease. For an increase, use a positive number. For a decrease, use a negative number. What is the change in the total cost for each book printed? \( \$ \square \)