[tex] \frac{3}{5} + \frac{1}{5} = \frac{3 + 1}{5} = \frac{4}{5} [/tex]
[tex] \frac{6}{13} + \frac{2}{13} = \frac{6 + 2}{13} = \frac{8}{13} [/tex]
[tex] \frac{22}{15} - \frac{9}{15} = \frac{22 - 9}{15} = \frac{13}{15} [/tex]
[tex] \frac{31}{21} - \frac{11}{21} = \frac{31 - 11}{21} = \frac{20}{21} [/tex]
