a) \(\frac{2 \cdot 7}{6 \cdot 5} = \frac{14}{30} = \frac{7}{15}, \frac{3 \cdot 5}{7 \cdot 3} = \frac{15}{21} = \frac{5}{7}, \frac{9 \cdot 4}{4 \cdot 7} = \frac{36}{28} = \frac{9}{7}, \frac{11 \cdot 5}{3 \cdot 11} = \frac{55}{33} = \frac{5}{3}\)
b) \(\frac{4 \cdot 3}{7 \cdot 8} = \frac{12}{56} = \frac{3}{14}, \frac{2 \cdot 3}{3 \cdot 10} = \frac{6}{30} = \frac{1}{5}, \frac{21 \cdot 6}{21 \cdot 7} = \frac{126}{147} = \frac{6}{7}\)