Đáp án:
a) `sqrt{frac{3}{20}}+sqrt{frac{1}{60}}-2sqrt{frac{1}{15}}`
`=frac{sqrt{3}}{2sqrt{5}}+frac{1}{2sqrt{15}}-2frac{1}{sqrt{15}}`
`=frac{sqrt{15}}{10}+frac{sqrt{15}}{30}-frac{2sqrt{15}}{15}`
`=frac{3sqrt{15}+sqrt{15}-4sqrt{15}}{30}`
`=0`
$\text{Shield Knight}$