$\frac{9³.8^{4}}{6^{9}.4^{2}}=\frac{3^{6}.2^{12}}{3^{9}.2^{9}.2^{4}}=\frac{3^{6}.2^{12}}{3^{9}.2^{13}}=\frac{1}{3^{3}.2}=\frac{1}{54}$
$\frac{9^{5}.27^{3}}{3^{18}}=\frac{3^{10}.3^{9}}{3^{18}}=\frac{3^{19}}{3^{18}}=3$
$(\frac{4}{15}:0,4):1,254^{0}=(\frac{4}{15}:\frac{2}{5}):1=\frac{4}{15}×\frac{5}{2}=\frac{2}{3}$