[tex]15 + \frac{1}{3} + 4 + \frac{2}{3} = (15 + 4) + ( \frac{1}{3} + \frac{2}{3}) = 19 + \frac{3}{3} = 19 + 1 = 20[/tex]
[tex]3 + \frac{2}{9} + 17 + \frac{7}{9 } = (3 + 17) + ( \frac{2}{9} + \frac{7}{9}) = 20 + \frac{9}{9} = 20 + 1 = 21[/tex]
[tex] \frac{14}{19} + \frac{2}{37} + \frac{5}{19} + \frac{35}{37} = ( \frac{14}{19} + \frac{5}{19} ) + ( \frac{2}{37} + \frac{35}{37} ) = \frac{19}{19} + \frac{37}{37} = 1 + 1 = 2[/tex]
