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$9 \frac{2}{7} -5 \frac{4}{6} =9 \frac{12}{42} -5 \frac{28}{42} =3 \frac{54-28}{42} =3 \frac{26}{42} =3 \frac{13}{21} \\\\ 7 \frac{1}{9} -5 \frac{7}{12} =7 \frac{4}{36} -5 \frac{21}{36} =1 \frac{40-21}{36} =1 \frac{19}{36} \\\\ 8 \frac{5}{9} -7 \frac{7}{10} =8 \frac{50}{90} -7 \frac{63}{90} = \frac{140-63}{90} = \frac{77}{90} \\\\ 9 \frac{2}{5} -6 \frac{5}{8} =9 \frac{16}{40} -6 \frac{25}{40} =2 \frac{56-25}{40}=2 \frac{31}{40}$