a)
4 * \sqrt{\frac{81}{16}} + 5 *\sqrt{\frac{64}{25}}-2*\sqrt[3]{\frac{27}{8}}=
4 * \frac{9}{4} + 5 * \frac{6}{5} - 2 * \frac{3}{2} = 9 + 6 - 3 = 12
b)
2*\sqrt{\frac{1}{25}}+3*\sqrt{\frac{4}{9}}-4*\sqrt{\frac{1}{4}}=2*\frac{1}{5}+3*\frac{2}{3} - 4 *\frac{1}{2} = \frac{2}{5} + 2 - 2 = \frac{2}{5}