[tex]a) \frac{2}{3} = \frac{3}{6} + \frac{1}{6} = \frac{4}{6} [/tex]
[tex]b) \frac{2}{3} = \frac{1}{9} + \frac{2}{9} + \frac{3}{9} = \frac{6}{9} [/tex]
[tex]c) \frac{2}{3} = \frac{1}{15} + \frac{2}{15} + \frac{3}{15} + \frac{4}{15} = \frac{10}{15} [/tex]