Incorrect. To simplify this expression, multiply the factors under the radical signs:

$\displaystyle{7}\sqrt{{{5}{{x}}^{{3}}}}\cdot{2}\sqrt{{{15}{{x}}^{{5}}}}={14}\sqrt{{{5}{{x}}^{{3}}\cdot{15}{{x}}^{{5}}}}={14}\sqrt{{{75}{{x}}^{{8}}}}\usepackage{cmbright}\Huge\$

Identify perfect square factors and rewrite as a product. Simplify using $\displaystyle\sqrt{{{{a}}^{{2}}}}={a}\usepackage{cmbright}\Huge\$ . The correct answer is 70.