[tex]a) \ \frac{6}{7} = \frac{6\cdot5}{7\cdot5} = \frac{30}{35} \ \ \ \ i \ \ \ \ \frac{4}{5} = \frac{4\cdot7}{5\cdot7} = \frac{28}{35}\\\\b) \ \frac{9}{10} = \frac{9\cdot6}{10\cdot6} = \frac{54}{60} \ \ \ \ i \ \ \ \ \frac{11}{12} = \frac{11\cdot5}{12\cdot5} = \frac{55}{60}[/tex]
[tex]c) \ \frac{5}{7} = \frac{5\cdot4}{7\cdot4} = \frac{20}{28} \ \ \ \ i \ \ \ \ \frac{6}{8} =\frac{3}{4} = \frac{3\cdot7}{4\cdot7} = \frac{20}{28}\\\\d) \ 6\frac{7}{9} = 6\frac{7\cdot13}{9\cdot13} = 6\frac{91}{117} \ \ \ \ i \ \ \ \ 6\frac{11}{13} = 6\frac{11\cdot9}{13\cdot9} = 6\frac{99}{117}[/tex]
