Explicação passo-a-passo:
[tex]a) \: 9 \times \frac{9}{7} = \frac{9}{1} \times \frac{9}{7} = \frac{81}{7} \\ b) \: 7 \times \frac{4}{7} = \frac{7}{1} \times \frac{4}{7} = \frac{28}{7} \\ c) \: \frac{5}{7} \times \frac{9}{2} = \frac{45}{14} \\ d) \: \frac{2}{3} \times \frac{5}{7} = \frac{10}{21} [/tex]
