2.11. Solve the equation

$$
3 \sqrt{x^{2}-9}+4 \sqrt{x^{2}-16}+5 \sqrt{x^{2}-25}=\frac{120}{x}
$$
2.11. The expression on the left side increases as $x$ increases, while the expression on the right side decreases. Therefore, the equation has no more than one solution. It is easy to verify that $x=5$ is a solution.