1.3. Вычислите: \(\frac{1}{2}-\frac{9}{10}\).

\(\frac{1}{2}=\frac{5}{10}\).

\(\frac{5}{10}-\frac{9}{10}=-\frac{4}{10}=-\frac{2}{5}\).

Ответ: \(-\frac{2}{5}\).