1. \( \frac{1}{2}+\frac{3}{4}-\frac{5}{8} \) 2. \( \frac{2}{3}+\frac{5}{6}-\frac{1}{2} \) 3. \( \frac{4}{5}-\frac{1}{10}+\frac{3}{20} \)

To solve the first expression \( \frac{1}{2}+\frac{3}{4}-\frac{5}{8} \), let's find a common denominator, which is 8. This gives us \( \frac{4}{8} + \frac{6}{8} - \frac{5}{8} = \frac{4 + 6 - 5}{8} = \frac{5}{8} \). For the second expression \( \frac{2}{3}+\frac{5}{6}-\frac{1}{2} \), the common denominator is 6. Rewriting gives \( \frac{4}{6} + \frac{5}{6} - \frac{3}{6} = \frac{4 + 5 - 3}{6} = \frac{6}{6} = 1 \). Lastly, for \( \frac{4}{5}-\frac{1}{10}+\frac{3}{20} \), the common denominator is 20. This becomes \( \frac{16}{20} - \frac{2}{20} + \frac{3}{20} = \frac{16 - 2 + 3}{20} = \frac{17}{20} \).