Compare the following fractions using symbols less than <, greater than >, =.

$$
\frac{1}{8} = \frac{1 \times 5}{8 \times 5} = \frac{5}{40}
$$
$$
\frac{2}{5} = \frac{2 \times 8}{5 \times 8} = \frac{16}{40}
$$

Since $5 < 16$, then $\frac{5}{40} < \frac{16}{40}$.  
Therefore, $\boxed{\frac{1}{8} < \frac{2}{5}}$.

$$
\frac{7}{9} = \frac{7 \times 2}{9 \times 2} = \frac{14}{18}
$$
$$
\frac{5}{6} = \frac{5 \times 3}{6 \times 3} = \frac{15}{18}
$$

Since $14 < 15$, then $\frac{14}{18} < \frac{15}{18}$.  
Therefore, $\boxed{\frac{7}{9} < \frac{5}{6}}$.

$$
\frac{2}{3} = \frac{2 \times 5}{3 \times 5} = \frac{10}{15}
$$
$$
\frac{3}{5} = \frac{3 \times 3}{5 \times 3} = \frac{9}{15}
$$

Since $10 > 9$, then $\frac{10}{15} > \frac{9}{15}$.  
Therefore, $\boxed{\frac{2}{3} > \frac{3}{5}}$.

$$
\frac{2}{3} = \frac{2 \times 2}{3 \times 2} = \frac{4}{6}
$$
$$
\frac{1}{2} = \frac{1 \times 3}{2 \times 3} = \frac{3}{6}
$$

Since $4 > 3$, then $\frac{4}{6} > \frac{3}{6}$.  
Therefore, $\boxed{\frac{2}{3} > \frac{1}{2}}$.

$$
\frac{4}{5} = \frac{4 \times 4}{5 \times 4} = \frac{16}{20}
$$
$$
\frac{3}{4} = \frac{3 \times 5}{4 \times 5} = \frac{15}{20}
$$

Since $16 > 15$, then $\frac{16}{20} > \frac{15}{20}$.  
Therefore, $\boxed{\frac{4}{5} > \frac{3}{4}}$.