a) $7^{3}$ . $7^{5}$
= $7^{3 + 5}$
= $ 7^{8}$
b) $(-2)^{5}$ . $(-2)^{6}$
= $(-2)^{5 + 6}$
= $(-2)^{11}$
c) $5^{6}$ . $5^{4}$
= $5^{6 + 4}$
= $5^{10}$
d) $(\frac{-7}{8})^{2}$ . $(\frac{-7}{8})^{3}$
= $(\frac{-7}{8})^{2 + 3}$
= $(\frac{-7}{8})^{5}$
e) ($\frac{3}{4}$) . $(\frac{-3}{4})^{4}$
= ($\frac{3}{4}$) . $(\frac{3}{4})^{4}$
= $(\frac{3}{4})^{4 + 1}$
= $(\frac{3}{4})^{5}$
f) $(-\frac{4}{5})^{5}$ . $(-\frac{4}{5})^{3}$
= $(-\frac{4}{5})^{5 + 3}$
= $(-\frac{4}{5})^{8}$
g) $\frac{(-18)³}{6^{4}}$
= $\frac{6³.(-3)³}{6^{4}}$
= $\frac{(-3)³}{6}$
= $\frac{(-3)³}{3.2}$
= $\frac{-(-3)²}{2}$
= $\frac{-9}{2}$
h) $\frac{9³}{81^{4}}$
= $\frac{9³}{9^{8}}$
= $\frac{1}{9^{5}}$
i) $\frac{21²}{(-7)^{4}}$
= $\frac{7².3²}{(7)^{4}}$
= $\frac{3²}{7²}$
= $\frac{9}{49}$
