Для того чтобы привести дроби к наименьшему общему знаменателю, нужно:
1)
$$\frac{3}{8}$$ и $$\frac{1}{6}$$;
НОК (8, 6) = 24.
$$\frac{3}{8} = \frac{3 \cdot 3}{8 \cdot 3} = \frac{9}{24};$$
$$\frac{1}{6} = \frac{1 \cdot 4}{6 \cdot 4} = \frac{4}{24}.$$
2)
$$\frac{4}{9}$$ и $$\frac{5}{6}$$;
НОК (9, 6) = 18.
$$\frac{4}{9} = \frac{4 \cdot 2}{9 \cdot 2} = \frac{8}{18};$$
$$\frac{5}{6} = \frac{5 \cdot 3}{6 \cdot 3} = \frac{15}{18}.$$
3)
$$\frac{2}{9}$$ и $$\frac{5}{18}$$;
НОК (9, 18) = 18.
$$\frac{2}{9} = \frac{2 \cdot 2}{9 \cdot 2} = \frac{4}{18};$$
$$\frac{5}{18} = \frac{5 \cdot 1}{18 \cdot 1} = \frac{5}{18}.$$
4)
$$\frac{4}{5}$$ и $$\frac{3}{8}$$;
НОК (5, 8) = 40.
$$\frac{4}{5} = \frac{4 \cdot 8}{5 \cdot 8} = \frac{32}{40};$$
$$\frac{3}{8} = \frac{3 \cdot 5}{8 \cdot 5} = \frac{15}{40}.$$
5)
$$\frac{5}{12}$$ и $$\frac{7}{18}$$;
НОК (12, 18) = 36.
$$\frac{5}{12} = \frac{5 \cdot 3}{12 \cdot 3} = \frac{15}{36};$$
$$\frac{7}{18} = \frac{7 \cdot 2}{18 \cdot 2} = \frac{14}{36}.$$
6)
$$\frac{7}{10}$$, $$\frac{5}{8}$$ и $$\frac{1}{4}$$;
НОК (10, 8, 4) = 40.
$$\frac{7}{10} = \frac{7 \cdot 4}{10 \cdot 4} = \frac{28}{40};$$
$$\frac{5}{8} = \frac{5 \cdot 5}{8 \cdot 5} = \frac{25}{40};$$
$$\frac{1}{4} = \frac{1 \cdot 10}{4 \cdot 10} = \frac{10}{40}.$$
Ответ: 1) $$\frac{9}{24}$$ и $$\frac{4}{24}$$, 2) $$\frac{8}{18}$$ и $$\frac{15}{18}$$, 3) $$\frac{4}{18}$$ и $$\frac{5}{18}$$, 4) $$\frac{32}{40}$$ и $$\frac{15}{40}$$, 5) $$\frac{15}{36}$$ и $$\frac{14}{36}$$, 6) $$\frac{28}{40}$$, $$\frac{25}{40}$$ и $$\frac{10}{40}$$