Решение задания 25.

a) \( \frac{5}{9} = \frac{10}{18} \), b) \( \frac{11}{16} = \frac{44}{64} \), c) \( \frac{1}{15} = \frac{6}{90} \), d) \( \frac{6}{7} = \frac{60}{70} \), e) \( \frac{12}{13} = \frac{36}{39} \), f) \( \frac{3}{4} = \frac{240}{320} \).