a) \(\dfrac{\left(-3\right)^{10}\cdot15^5}{25^3\cdot\left(-9\right)^7}\)
\(=-\dfrac{3^{10}\cdot3^5\cdot5^5}{5^6\cdot3^{14}}\)
\(=\dfrac{-3}{5}\)
b: \(\dfrac{4^{30}\cdot3^{43}}{2^{57}\cdot27^{15}}\)
\(=\dfrac{2^{60}\cdot3^{43}}{2^{57}\cdot3^{45}}\)
\(=8\cdot\dfrac{1}{9}=\dfrac{8}{9}\)