Explicação passo-a-passo:
[tex](a × b) + (a - b) \\ = ( \frac{5}{7} \times \frac{7}{13} ) + ( \frac{5}{7} - \frac{7}{13} ) \\ = ( \frac{35}{91} ) + ( \frac{13 \times 5}{91} - \frac{7 \times 7}{91} ) \\ = \frac{35}{91} + ( \frac{65}{91} - \frac{49}{91} ) \\ = \frac{35}{91} + ( \frac{16}{91} ) \\ = \frac{51}{91} [/tex]
