[tex]1- \frac{3}{7} = \frac{7}{7} - \frac{3}{7}= \frac{7-3}{7} = \frac{4}{7}
[/tex]
[tex]7 \frac{3}{10} -3 \frac{7}{15} = \frac{7*10+3}{10} + \frac{3*15+7}{15} = \frac{73}{10} + \frac{52}{15} = \frac{3*73+52*2}{30} = \frac{323}{30} [/tex]
[tex] \frac{17}{18} - \frac{4}{9} - \frac{1}{6} = \frac{17-4*2-3*1}{18} = \frac{17-11}{18} = \frac{6}{18} = \frac{1}{3} [/tex]
