7) \(\frac{2}{5} - \frac{1}{10} = \frac{4}{10} - \frac{1}{10} = \frac{3}{10} = 0,3\)

Решение:

\(\frac{2}{5} - \frac{1}{10} = \frac{2 \cdot 2}{5 \cdot 2} - \frac{1}{10} = \frac{4}{10} - \frac{1}{10} = \frac{4-1}{10} = \frac{3}{10}\)

Ответ: \(\frac{3}{10}\)