If you had $\displaystyle\sqrt{{3}}\cdot\sqrt{{3}}\usepackage{cmbright}\Huge\$ , this would simplify to 3. However, in the given expression the square roots are not being multiplied. In these radical terms, the radicals themselves are the same; both are square roots and both radicands are 3. This means that you have like terms. Combine them just as you would combine $\displaystyle{8}{a}+{2}{a}\usepackage{cmbright}\Huge\$ .