\(\left(\frac{1}{81}\right)^{25}:\left(\frac{1}{3}\right)^{30}=\left[\left(\frac{1}{3}\right)^4\right]^{25}:\left(\frac{1}{3}\right)^{30}=\left(\frac{1}{3}\right)^{100}:\left(\frac{1}{3}\right)^{30}=\left(\frac{1}{3}\right)^{100-30}=\left(\frac{1}{3}\right)^{70}\)
\(\left(\frac{1}{81}\right)^{25}:\left(\frac{1}{3}\right)^{30}=\left[\left(\frac{1}{3}\right)^4\right]^{25}:\left(\frac{1}{3}\right)^{30}=\left(\frac{1}{3}\right)^{100}:\left(\frac{1}{3}\right)^{30}=\left(\frac{1}{3}\right)^{100-30}=\left(\frac{1}{3}\right)^{70}\)