Ответ:
\(\frac{2}{5}-\frac{3}{8}=\frac{16}{40}-\frac{15}{40}=\frac{1}{40}\).
\(\frac{1}{8}+\frac{21}{10}=\frac{5}{40}+\frac{84}{40}=\frac{89}{40}\).
Следовательно, \(\frac{2}{5}-\frac{3}{8}<\frac{1}{8}+\frac{21}{10}\).
\(\frac{2}{5}-\frac{3}{8}=\frac{16}{40}-\frac{15}{40}=\frac{1}{40}\).
\(\frac{1}{8}+\frac{21}{10}=\frac{5}{40}+\frac{84}{40}=\frac{89}{40}\).
Следовательно, \(\frac{2}{5}-\frac{3}{8}<\frac{1}{8}+\frac{21}{10}\).