Simplify the last term using $\displaystyle\sqrt{{{a}{b}}}=\sqrt{{a}}\cdot\sqrt{{b}}\usepackage{cmbright}\Huge\$ :

$\displaystyle{9}\sqrt{{{x}}}+{2}{\sqrt[{{3}}]{{{x}}}}+\sqrt{{{4}{x}}}={9}\sqrt{{x}}+{2}{\sqrt[{{3}}]{{{x}}}}+\sqrt{{4}}\cdot\sqrt{{x}}={9}\sqrt{{x}}+{2}{\sqrt[{{3}}]{{{x}}}}+{2}\sqrt{{x}}\usepackage{cmbright}\Huge\$

The first and third terms are like terms and can be combined:

$\displaystyle{9}\sqrt{{x}}+{2}\sqrt{{x}}={\left({9}+{2}\right)}\sqrt{{x}}={11}\sqrt{{x}}\usepackage{cmbright}\Huge\$

So the entire expression equals $\displaystyle{11}\sqrt{{{x}}}+{2}{\sqrt[{{3}}]{{{x}}}}\usepackage{cmbright}\Huge\$ . Because the indices are not the same, this cannot be further simplified.