a: \(=\left(2\sqrt{3}+3\sqrt{3}-4\sqrt{3}\right)\cdot\sqrt{3}\)
\(=\sqrt{3}\cdot\sqrt{3}=3\)
b: \(=\sqrt{\dfrac{16}{9}\cdot\dfrac{8.1}{4}\cdot\dfrac{90}{25}}=\sqrt{\dfrac{16}{9}\cdot\dfrac{81}{4}\cdot\dfrac{9}{25}}\)
\(=\sqrt{\dfrac{16}{25}\cdot\dfrac{81}{4}}=\dfrac{4}{5}\cdot\dfrac{9}{2}=\dfrac{36}{10}=\dfrac{18}{5}\)
c: \(=\sqrt{\dfrac{25}{16}\cdot\dfrac{49}{9}\cdot\dfrac{1}{100}}=\dfrac{5}{4}\cdot\dfrac{7}{3}\cdot\dfrac{1}{10}=\dfrac{35}{120}=\dfrac{7}{24}\)
d: \(=\sqrt{\dfrac{\left(149-76\right)\left(149+76\right)}{\left(457-384\right)\left(457+384\right)}}=\sqrt{\dfrac{225}{841}}=\dfrac{15}{29}\)