Factor to find variables with even exponents: $\displaystyle\sqrt{{{{r}}^{{4}}\cdot{r}\cdot{{s}}^{{14}}\cdot{{t}}^{{6}}\cdot{t}}}\usepackage{cmbright}\Huge\$

Rewrite those as squares: $\displaystyle\sqrt{{{{\left({{r}}^{{2}}\right)}}^{{2}}\cdot{r}\cdot{{\left({{s}}^{{7}}\right)}}^{{2}}\cdot{{\left({{t}}^{{3}}\right)}}^{{2}}\cdot{t}}}\usepackage{cmbright}\Huge\$

Separate the squares into individual radicals: $\displaystyle\sqrt{{{{\left({{r}}^{{2}}\right)}}^{{2}}}}\cdot\sqrt{{{{\left({{s}}^{{7}}\right)}}^{{2}}}}\cdot\sqrt{{{{\left({{t}}^{{3}}\right)}}^{{2}}}}\cdot\sqrt{{{r}\cdot{t}}}\usepackage{cmbright}\Huge\$

Find square roots. Use absolute value for odd exponents: $\displaystyle{{r}}^{{2}}\cdot{\left|{{s}}^{{7}}\cdot{{t}}^{{3}}\right|}\cdot\sqrt{{{r}\cdot{t}}}\usepackage{cmbright}\Huge\$

Simplify: $\displaystyle{{r}}^{{2}}{\left|{{s}}^{{7}}{{t}}^{{3}}\right|}\sqrt{{{r}{t}}}\usepackage{cmbright}\Huge\$