1. 3/8 + 5/8
\[ \frac{3}{8} + \frac{5}{8} = \frac{3+5}{8} = \frac{8}{8} = 1 \]
2. 3 5/9 - 2 4/9
\[ 3\frac{5}{9} - 2\frac{4}{9} = \left(3 - 2\right) + \left(\frac{5}{9} - \frac{4}{9}\right) = 1 + \frac{1}{9} = 1\frac{1}{9} \]
3. 1 - 4/11
\[ 1 - \frac{4}{11} = \frac{11}{11} - \frac{4}{11} = \frac{11-4}{11} = \frac{7}{11} \]
4. 2/10 + 7/10
\[ \frac{2}{10} + \frac{7}{10} = \frac{2+7}{10} = \frac{9}{10} \]
5. 5 - 2 2/7
\[ 5 - 2\frac{2}{7} = \left(4 + \frac{7}{7}\right) - 2\frac{2}{7} = \left(4 - 2\right) + \left(\frac{7}{7} - \frac{2}{7}\right) = 2 + \frac{5}{7} = 2\frac{5}{7} \]
6. 1 2/5 + 2 1/5
\[ 1\frac{2}{5} + 2\frac{1}{5} = \left(1 + 2\right) + \left(\frac{2}{5} + \frac{1}{5}\right) = 3 + \frac{3}{5} = 3\frac{3}{5} \]
7. 11/15 + 4/15
\[ \frac{11}{15} + \frac{4}{15} = \frac{11+4}{15} = \frac{15}{15} = 1 \]
8. 7 3/13 - 3/13
\[ 7\frac{3}{13} - \frac{3}{13} = 7 + \left(\frac{3}{13} - \frac{3}{13}\right) = 7 + 0 = 7 \]
9. 1 5/7 + 4/7
\[ 1\frac{5}{7} + \frac{4}{7} = 1 + \left(\frac{5}{7} + \frac{4}{7}\right) = 1 + \frac{9}{7} = 1 + 1\frac{2}{7} = 2\frac{2}{7} \]
10. 1 3/9 + 2
\[ 1\frac{3}{9} + 2 = \left(1 + 2\right) + \frac{3}{9} = 3 + \frac{3}{9} = 3\frac{3}{9} = 3\frac{1}{3} \]
11. 5 5/7 - 2
\[ 5\frac{5}{7} - 2 = \left(5 - 2\right) + \frac{5}{7} = 3 + \frac{5}{7} = 3\frac{5}{7} \]
12. 1 2/9 + 2/9 + 1 6/9
\[ 1\frac{2}{9} + \frac{2}{9} + 1\frac{6}{9} = \left(1 + 1\right) + \left(\frac{2}{9} + \frac{2}{9} + \frac{6}{9}\right) = 2 + \frac{2+2+6}{9} = 2 + \frac{10}{9} = 2 + 1\frac{1}{9} = 3\frac{1}{9} \]
13. 1 3/8 - 5/8
\[ 1\frac{3}{8} - \frac{5}{8} = \frac{11}{8} - \frac{5}{8} = \frac{11-5}{8} = \frac{6}{8} = \frac{3}{4} \]
14. 7/8 + 3/8
\[ \frac{7}{8} + \frac{3}{8} = \frac{7+3}{8} = \frac{10}{8} = \frac{5}{4} = 1\frac{1}{4} \]
15. 2 5/6 - 5/6
\[ 2\frac{5}{6} - \frac{5}{6} = \left(1 + \frac{6}{6}\right) + \frac{5}{6} - \frac{5}{6} = 1 + \frac{6}{6} = 1 + 1 = 2 \]
16. 1 1/3 + 1 1/2
\[ 1\frac{1}{3} + 1\frac{1}{2} = \left(1+1\right) + \left(\frac{1}{3} + \frac{1}{2}\right) = 2 + \left(\frac{2}{6} + \frac{3}{6}\right) = 2 + \frac{5}{6} = 2\frac{5}{6} \]
17. 3 2/5 + 2/3
\[ 3\frac{2}{5} + \frac{2}{3} = 3 + \left(\frac{2}{5} + \frac{2}{3}\right) = 3 + \left(\frac{6}{15} + \frac{10}{15}\right) = 3 + \frac{16}{15} = 3 + 1\frac{1}{15} = 4\frac{1}{15} \]
18. 7 1/8 - 1/2
\[ 7\frac{1}{8} - \frac{1}{2} = 7\frac{1}{8} - \frac{4}{8} = \left(6 + \frac{8}{8}\right) + \frac{1}{8} - \frac{4}{8} = 6 + \frac{9}{8} - \frac{4}{8} = 6 + \frac{5}{8} = 6\frac{5}{8} \]
19. 2 2/5 + 2/3 + 3/4
\[ 2\frac{2}{5} + \frac{2}{3} + \frac{3}{4} = 2 + \left(\frac{2}{5} + \frac{2}{3} + \frac{3}{4}\right) = 2 + \left(\frac{24}{60} + \frac{40}{60} + \frac{45}{60}\right) = 2 + \frac{109}{60} = 2 + 1\frac{49}{60} = 3\frac{49}{60} \]
20. 3 5/20 - 4/20 - 1 6/20
\[ 3\frac{5}{20} - \frac{4}{20} - 1\frac{6}{20} = \left(3 - 1\right) + \left(\frac{5}{20} - \frac{4}{20} - \frac{6}{20}\right) = 2 + \frac{5-4-6}{20} = 2 + \frac{-5}{20} = 2 - \frac{5}{20} = 2 - \frac{1}{4} = 1\frac{3}{4} \]