Câu 1:
a) $\frac{88}{64}$=$\frac{11}{8}$=$\frac{55}{40}$=$\frac{110}{80}$
b) $\frac{56}{72}$=$\frac{238}{306}$=$\frac{7}{9}$=$\frac{63}{81}$
Câu 2:
a) ( $\frac{1}{2}$ +$\frac{1}{3}$)×$\frac{2}{5}$=$\frac{5}{6}$ ×$\frac{2}{5}$=$\frac{1}{3}$
b) $\frac{4}{5}$ ×$\frac{6}{7}$×2=$\frac{24}{35}$×2=$\frac{48}{35}$