[tex]a) \frac{7}{9} - \frac{2}{9} = \frac{7 - 2}{9} = \frac{5}{9} [/tex]
[tex]b) \frac{15}{9} - \frac{10}{9} = \frac{15 - 10}{9} = \frac{5}{9} [/tex]
[tex]c) \frac{10}{9} - \frac{3}{9} - \frac{2}{9} = \frac{10 - 3 - 2}{9} = \frac{7 - 2}{9} = \frac{5}{9} [/tex]