Приведите к наименьшему общему знаменателю дроби: a) $$9/20$$ и $$6/35$$ б) $$11/14$$ и $$11/42$$ в) $$13/12$$ и $$5/9$$

а) $$9/20$$ и $$6/35$$; НОК (20, 35) = 140

• $$9/20 = (9 \times 7)/(20 \times 7) = 63/140$$
• $$6/35 = (6 \times 4)/(35 \times 4) = 24/140$$

б) $$11/14$$ и $$11/42$$; НОК (14, 42) = 42

• $$11/14 = (11 \times 3)/(14 \times 3) = 33/42$$
• $$11/42 = (11 \times 1)/(42 \times 1) = 11/42$$

в) $$13/12$$ и $$5/9$$; НОК (12, 9) = 36

• $$13/12 = (13 \times 3)/(12 \times 3) = 39/36$$
• $$5/9 = (5 \times 4)/(9 \times 4) = 20/36$$