a) 2³ : 2² = $2^{3-2}$ = $2^{1}$
b) $(\frac{-3}{4})^{4}$ : $(\frac{3}{4})^{5}$ = $(\frac{3}{4})^{4}$ : $(\frac{3}{4})^{5}$ = $(\frac{3}{4})^{4-5}$ = $(\frac{3}{4})^{-1}$
c) $(\frac{7}{9})^{6}$ : $(\frac{-7}{9})^{3}$ = $(\frac{-7}{9})^{6}$ : $(\frac{-7}{9})^{3}$ = $(\frac{-7}{9})^{6-3}$ = $(\frac{-7}{9})^{3}$
Chúc học tốt!!!